Saturday, 12 May 2018

Jupiter - transit of Europa and its shadow animation

Hello everyone,

The day following my Jupiter sketch I revisited Jup’ and saw the last few minutes of the shadow transit of Io.  With this being essentially the time of Jupiter’s opposition, the gap between Io and its shadow on Jupiter’s disk is just about nil.  As a result it is actually very easy to spot Io against the disk of Jupiter when it is very close to the limb.  This really excite me, and I was keen to sketch the event when it repeated itself.

A couple of nights later (poor seeing conditions prevented any possible sketching), Europa was to transit across Jupiter along with its shadow.  The passing of just four nights was already enough to make the gap between the satellite and its shadow larger, but the effect was really just as intense and fantastic.

 As the transit of Europa started, it occurred to me that I could possibly do an animation of the event out of a series of sketches.  So, two and a bit hours later, I had a completed a sketch with the necessary details and time points that would allow me to prepare a series of twelve individual colour pencil sketches.

Below is the complete series of individual sketches from which the animation was made.

Normally for a high magnification sketch I would have used my 8” SCT.  This time however I used my 8” f/4 Kulali push-pull dob.  Its action is so smooth and easy that following an object at high magnification is very easy.

Object:  Jupiter with transit of Europa and its shadow
Scope:  8” f/4 Kulali push-pull dob
Gear:  5mm TMB Planetary Type II, 160X
Date:  9th May, 2018, 21:10 to 23:20 AET
Location:  Sydney, Australia

Thanks for looking,


Saturday, 5 May 2018

Jupiter - good conditions and a newer scope reveals remarkable detail

Hello everyone,

Well, after so long, I’ve managed reasonable seeing conditions to attempt a sketch of Jupiter.  Last year was a complete non-event with Jupiter as no matter when I looked at Jupiter, seeing was just terrible.  In fact, I haven’t managed a sketch of Jupiter in many years.

I do have to say that one big part of this was due to the old orange tube C8 I was using at the time just wasn’t up to the task.  In terms of focus, that old scope was remarkable and outstanding.  But she didn’t have coated optics, and being close to 40 years old, the optics were not as reflective as when new.  With the Moon this wasn’t an issue, but for planetary detail she wasn’t the best tool for the job.  The new SCT I’m now using, well, there is a big difference!  I am fortunate that the optics are also very good with this new unit, and I can pull outstanding detail with it at high magnification, but the optics are multicoated, and this has made an enormous difference for planetary detail and with DSO’s.

Well, it was good to have a break in the poor seeing and have the opportunity to not only pin Jupiter, but to also try a few illustration techniques I’ve been wanting to have a go with.

As with all my sketching, the longer I spend on a target, the more and more I see as time goes on.  Jupiter was no exception.  As clear seeing windows wafted through, these details revealed themselves as festoons, smaller pressure cells within the two main belts, a mottled structure within the fine bands, subtle colour variations within all the band structures, and most staggering of all was the significant hue difference and structural differences between the two main belts – something that I hadn’t noticed in photographs.  I've also noted the position of the four Galilean moons with just the first letter of the name of each.

Again, the best eyepiece for the night was my modest 9mm TMB Planetary Type II.  My 8mm LVW was just too much grunt, and the TMB just gave a longer and more frequent detail sweet spot as seeing came and went.  I also use two colour filters to help tease out details, a #80A blue and a #8 yellow.  The blue was excellent to tease out the Great Red Spot and the fine cloud banding. The yellow was especially helpful in highlighting the hue differences between the two main cloud bands and the subtle colour variations between the fine bands too.

The sketch at the scope was carried out using a good old graphite pencil on white paper, with a few notes added.  In the light of day I redid the sketch using a variety of coloured pencils on fine white paper – the fine texture paper is important in order to control the scratchy appearance drawing onto paper can have.  Once I was happy with the colour sketch, I cut out the disk and stuck it onto a sheet of the black paper I use for sketching the Moon, Sun and DSO’s.  I think I may need to improve my scissor cutting skills a little! LOL J  I am very happy with the final sketch construct as it gives a better rendition of what is seen through the eyepiece.

Thanks for viewing this piece of mine.


Object:  Jupiter
Scope:  8” SCT
Gear:  9mm TMB, 222X, #80A blue and #8 yellow filters
Date:  4th May, 2018 14:00hrs UTC
Location:  Sydney,  Australia
Media:  Colour and graphite pencils on fine white paper, cut out and stuck onto black A4 size paper.

Crater Humboldt - still so much to learn!

Hi all,

My golly josh!  It has been some 5 months since my last lunar sketch!  This summer has been terrible with astro weather.  Finally there’s been a break in the weather!  Woohoo!

I’ve been wanting to sketch the eastern limb of the Moon from just after the full Moon phase for a very long time.  It is really the only opportunity to sketch features that otherwise are only visible very soon after the New Moon phase, which is not practical being too close to the Sun and the sky is still too bright for good contrast in the image.  On this occasion, the phase was just one day after Full Moon.

It was like looking at the Moon for the very first time!  The whole eastern limb of the Moon is packed full of features that I hadn’t seen before!  It was quite a revelation for me to find out that there was a whole section of the Moon that I was totally unfamiliar with.

This night I took a different approach on what to select to sketch as I couldn’t decide between three or four different areas.   One particular big crater caught my attention, Humboldt.  What most caught my attention is the curious set of central peaks.  So, I looked up Humboldt on the net, and was met with a staggering image from the Lunar Reconnaissance Orbiter – the floor of Humboldt is riddled with a most regular lacy pattern network of riles.  I have never seen such a regular pattern in any crater.  Along with the curious set of central peaks, I was sold on Humboldt as being the center piece of my first lunar sketch in several months.

I was rusty, very rusty to start with.  Not having sketched the Moon for so long, I struggled a little at first to find my grove with the foreshortening and then the shading.  But I persisted and eventually things started to flow and happen a lot more easily.

I found this area quite intriguing.  Humboldt itself is an extremely old feature, yet it’s somehow managed to avoid too much damage over the eons.  Quite remarkable really considering its location so close to the far side of the Moon that has taken the lion’s share of impacts.  Being so close to the limb, and with the terminator just creeping away from the limb, the shadows of the craters, mountains, lone peaks and ridges all made for an outstanding scene and composition to tackle.

While researching this crater after completing the sketch, I came across the site for the Lunar Reconnaissance Orbiter.  The site contains some very high resolution images of Humboldt along with an explanation for the cause of very curious pattern of riles.  As it turns out, these are fracture lines caused by the subterranean magma pressure causing the floor of Humboldt to dome.  From the LROC photograph below, one can see that the pattern of fracture lines is of-center to the geometric center of Humboldt.  This is because the crown of the dome is not centered either.

LROC image.

This sketch was a lovely way to blow the cobwebs out and get back into the grove of some sketching.  Fingers crossed it won’t be another five months until the next!

Object:  Crater Humboldt and surrounds
Telescope:  8” SCT
Gear:  9mm TMB, 222X
Date:  1st May, 2018
Location:  Sydney, Australia

Until next time,

Clear skies and sharp pencils,


Tuesday, 17 April 2018

Jazzing up Open Clusters

Hi everyone,

This year has been very lean pickings.  So my apology for the poor frequency of posts.

Of all the deep sky objects, open clusters have proven to be the most difficult to lay down in a way that conveys the sparkle that we see through the eyepiece.  This has been the main reason why I’ve avoided sketching them.

This last Sunday, the sky for once was remarkably clear hear at home, despite the warm day and smoke from major bushfires happening in southern Sydney.  With the Southern Cross being high up early in the evening, I thought it would be a good opportunity to experiment a little with some open clusters and trying to work out some ways to add that sparkle.

There are two magnificent open clusters that are bright and spectacular.  IC 2602 is also known as the Southern Pleiades, is very bright and large cluster just south of Eta Carina.  IC 2606 is just over 1.5° in diameter.  NGC 4755, the Jewel Box, is a gorgeous bright and compact cluster in the Southern Cross.  Its name comes from the lovely colours of white and red that can be seen in the component stars.

I sketched each in turn and photographed each before attempting some jazzing up techniques.  Through the eyepiece, these are quite spectacular clusters.  Being located in the band of the Milky Way, there is a certain background glow that goes to brightening the background, and adds to the pizzazz of the image.  The longer you spend looking at these clusters, the more and more stars you begin to make out as your eye adapts to the view.  It really is quite amazing.

So here are the two clusters.  And as always they appear as just dots on a black page…  <sigh>

Now, how to give some lift to these?

I’ve tried two techniques here.  The first is a very soft application of soft pastel dust to the cluster (Jewel Box), or around the individual component brilliant component stars (Southern Pleiades).  Ok, a little better, but still not enough.  Next, I added something I rarely ever use – the dreaded Ring Of Death… a field of view circle.  Yet this alone isn’t enough to convey the glow that is seen through the eyepiece.  So here I added another soft dusting all around the inside of the field of view circle, being careful to make it fade out coming into the field of view and not be too wide.  The idea here is to lift the overall image as it appears through the eyepiece, but not make too much impact on the cluster itself.  The trick being in the control in application of the dust around the circle.  The application of the dust on the cluster itself also needs to be very careful or it could come across as nebulosity instead of a wee lift in overall brilliance.

So, what do you think?  Any suggestions?

Difficult to convey through digital media, but hopefully the differences can be noticed.

Object:  IC 2606, The Southern Pleiades                         Object:  NGC 4755, The Jewel Box
Telescope:  8” f/4 push-pull dob                                       Telescope:  8” f/4 push-pull dob
Gear:  24mm 82° eyepiece, 33X                                       Gear:  10mm 70° eyepiece, 80X
Location:  Sydney, Australia                                             Location:  Sydney, Australia
Date:  15th April, 2018                                                      Date:  15th April, 2018

Thanks for looking,


Sunday, 4 February 2018

Dew Control With Astronomical Sketching

This has been one of the most confounded exercises for astro sketchers.  There have been lots of ideas, but few effective solutions.

For any solution, there should be a set of criteria that needs to be met:

·       *   Simple to make
·       *   Simple to use
·       *   Modest in power requirements
·       *   Be effective in keeping paper dry

Not an onerous set of requirements, but these have proven difficult to achieve.

This article will describe my experiences with dew and sketching, and the three solutions I’ve found that have proven most effective in controlling dew during my astro sketching sessions.  As they say, “necessity is the Mother of invention”.  Sometimes however, these solutions can have flippant origins!

Avoid dew to begin with!
The easiest solution requires no specialized equipment at all.  Careful site selection can provide an environment that is dew free in the first place all night long.  Dew and astronomy DO NOT need to be inseparable bed fellows.  It is possible to actually find locations that are dew free.  It does require knowing what to look for in the first place, and then to use this knowledge to finding the site.  A big grassy field is actually the WORST possible situation for any astro activities.  Grass means rich moist soil, and at night moisture saturation is quickly achieved with water vapour being released by the grass itself and from the soil, and dew settles very quickly as it is denser than air, and everything becomes very wet very quickly.  There are even some popular astro sites that have had no appropriate site selection processes carried out to fully determine the location’s suitability for astro activities.

However, it is possible to find dew free locations, if only being seasonal.  The dark site locations my observing bubbies and I use have been painstakingly vetted for exactly this purpose, and these 19 times out of twenty are perfectly dew free during our dark sky sessions.  On those rare occasions when dew does form, it also means that transparency is not as good as it can be, and usually we end up packing up early.

That’s another thing that dew affects.  The increase local water content in the air also reduces transparency.  Finding a dew free location has many more added benefits than just no dew – it also brings with it improved transparency, and it can also bring improved seeing depending on the local geographic surrounds.

You will find information on how to start looking for dew free locations in an article I wrote on the topic:

Dew shield solution
However, sometimes dew is unavoidable, no matter what we do.  I have been able to deal with modest amounts of dew with the very first sketching rig I made.  My first solution followed the simple “dew shield” principle and I created an awning that wraps around the sketch rig.  Very simple and effective as dew tends to fall around the paper largely without making the paper damp.  This awning also provides a great location from which to perch the lights by which I sketch. 

The location of the light source is also extremely important.  The worst location for the lighting is on top of one's head!  With the light being square to the paper, the reflected glare that comes off the paper goes wholly into one's eyes!  By having the paper being illuminated from the side, whatever glare there is is reflected straight off the side, and an absolute minimum of glare is reflected into one's eyes.

Fans and localised evaporation
Yet this initial simple solution has its limitations.  When the sketch exceeds A3 in size or when dew is particularly heavy, the simple awning just doesn’t provide enough protection.

I encountered this when I made my second sketching rig to accommodate a very large sheet of card to sketch the Large Magellanic Cloud.  The first night I used this rig, dew was very, very light, but the absorbing properties of the paper meant that it became damp very quickly, despite the larger awning I made for the rig.  I had to find another solution or this sketch would be impossible to do.

Using fans to cool and control dew on telescopes is very common place, and when implemented correctly can be extremely effective.  I had several 4” 12V fans at home that I had accumulated over the years as part of experiments with my scopes and from cannibalising them from old computers.  Running out of time and options, and having nothing to lose, a somewhat flippant idea came to me to install a couple of these fans to the top of the sketch rig.  To improve airflow efficiency and flow direction, I enclosed the fans with some thin black foam rubber.  For this initial iteration, I connected the fans in series.  Using a 12V power supply, this would mean a slower fan rpm rate, but I had to start somewhere.  If the initial testing proved positive, I could always reconnect the fans in parallel to increase the fans rpm’s and increase airflow.

Finally, the night came when dew was problematic, with my paper becoming damp very quickly.  I had no alternative but to switch on the fans and see what happened.

WOW!  These fans were so very effective!  Not only did they stop dew from dampening the paper, but they also dried out the damp that had already been absorbed by the paper!  On this particular night, EVERYTHING became wet from dew.  Our cars, telescopes, the ground, even my headlamp.  Yet the modest rpm’s that these fans were working at proved totally effective in keeping my paper absolutely bone dry.  It would have been impossible to work for three hours on the sketch that night if the paper wasn’t kept dry.  Damp paper leaves the paper very fragile and impossible to work with.  Just think of attempting to write on damp newspaper – an impossible task without causing damage to the paper, no matter how careful one is.

One other solution
Some people have suggested making a heated sketch pad.  The biggest problems with this is it means a huge power requirement that only gets larger as the sketch pad becomes larger.  It also means a more complicated fabrication, and it is not cost effective, nor simple to use.  I quickly discounted this as a viable solution.

This has been my journey so far in finding an effective dew control rig form my astro sketching.  When a sketch at the eyepiece can take anywhere between half an hour to nine hours, I really need to be able to have an extremely effective way to prevent my paper from becoming damp.  I now have three solutions – a dew free observing site, a simple awning reaching over my paper, and a fan powered sketching rig.  I hope this has given you some solutions and inspired so ideas for you to explore in your own astro sketching journey.


Tuesday, 30 January 2018

Large Magellanic Cloud sketch - completed, challenges & revelations, part III

Hello everyone,

Well, it’s taken close to a year, but I’ve finally managed to complete this HUGE sketch of the Large Magellanic Cloud for Prof. Renée James!  AND I found a system that helps keep my paper DRY during dewy nights!

First the weather conspired to prevent any chance of an early completion, by which time the LMC season had finished.  I had to wait until November last year for the new LMC season to begin, and the weather AGAIN delayed any chance of a favourable sketching night until two weeks ago.  I had left the sketch last year with the majority of the nebulosity laid down.  I then had the opportunity in mid-January for two crystal clear nights in which to complete the task.

If you recall, I had constructed a sketching rig especially for this size sheet.  The size of the sheet I used with this sketch measures 510mm X 635mm.  To the top of this rig I attached a pair of 100mm fans which I connected in series and runs on 12V.  I attached the fans more only because I had them and I thought I had nothing to lose if I try this idea.  On the second night of the sketch, conditions were very clear, but the easterly breeze that was blowing in from the coast meant that dew was forming a couple of hours after sunset, and my paper was beginning to dampen.  So I turned on the fans.  To my great surprise, the fans blew dry the damp and kept the paper bone dry the whole time I was sketching, while everything around us was getting soaked with dew!

I am absolutely overjoyed at this dew control find!  Sketching in dewy conditions has always been a problem for me, and I just abandoned the exercise as it is impossible to work with damp paper.  This system that I rigged up on a dumb whim of speculation proved to be the champion I needed to keep my paper dry and me working!  If it were not for this sketch, I would never have found this solution.  Thank you Renée!

As I had the fans connected in series, each fan was effectively running on 6V, and their spin velocity was lower than if they were running on 12V.  Yet this air flow was plenty to dry off the paper and keep it dry.  Connecting the fans in parallel would give me greater air flow, which could be advantageous when dew is very heavy, but at the same time, if dew is this heavy transparency would also be greatly diminished and less than ideal visibility.  But it is something to consider and explore.

The sketch I have to say I am greatly relieved that it is done.  The sketch presented serval technical challenges that I had to constantly keep on top of.  The scope I used was a 100mm f/5 achromatic refractor with a 30mm 82˚ eyepiece giving 17X magnification, and a true field of view of 5˚.  The LMC measures some 12˚ X 12˚, no less than 6 times the diameter of the full Moon, and nearly 3 times the true field of view given by my scope/eyepiece combination.  The single biggest challenge was maintaining the scale of the piece and the relative positions of the stars to each other.  Another challenge was keeping track of the different landmarks so I could position the different features in their correct position, stars and nebulosity the same.

There was another revelation that I found, though not as a result of this sketch, but of something else I’ve been thinking about – illumination of my work.

I REALLY dislike red light.  It is synonymous with astronomy the use of red light, but the reality is that the use of red light in astronomy is entirely a throwback to the old dark room days when red light was use to process black and white photographic prints.  The problem with red light is our human eyes are not great in making out detail when the only source is a feeble red light.  To make out any detail, such as reading a chart or finding something in your kit bag, the brilliance needs to be increased and increased and this begins to stuff up your night vision.  I for one really struggle to read my charts under red light, and my smartphone I run with the full colour display, not the “red light display”, as it is impossible to effectively read a dimly illuminated red coloured screen.  Red is a lousy colour for our human eyes to register contrast with.

Yet, if we slightly shorten the wavelength of the light we are using, we can reduce the brilliance of the light, gain a marked improvement in contrast when reading, and not compromise our dark adaptation – this was the thinking I had, and there was only one way to prove this, by trying it out.

The size of this LMC sketch meant that I was positioned further away from the paper than I would be otherwise.  Making out the pinpoints of the stars I was laying down with red light was impossible to see – all because our eyes are poor in making out contrast under red light.  I had no choice but to try out the amber light.

What a difference it made, instantly!  These amber LEDs are less brilliant than the red ones of the lamp I use for my sketching.  Yet I was able to easily and clearly make out EVERY pinpoint I was marking on the paper.  As for my dark adaptation and perception through the eyepiece?  No issues whatsoever!  I experienced no diminished dark adaptation at all.  Instead, because the light I’m using is now less brilliant, I have noticed my eyes are less stunned, and this only improves my seeing.

I will be writing a separate blog entry about the use of orange and amber lights.  There I will discuss in more detail the problems of red light, and the improvements that there are to gain by changing our mindset of “red lights only in astro” to instead a mindset that better takes into consideration our HUMAN eyes and the ways that we can better work with them instead of against them.

Once the work out in the field was completed, at home in the light of day I tidied up the sketch and touched up the piece to add those infinitely tiny and impossible to individually lay down tiniest of stars that as a whole lend their light to the overall visual appearance of the LMC.  I used the same “machine gun” device I use with globular clusters to give the necessary lift and life to the LMC.  Without these the sketch remains flat and lacking the necessary brilliance seen through the eyepiece.  I’ve added a close up of the bar and Tarantula nebula section to show this detail that the whole of sketch photo just cannot reveal.

So, here it is.  My rendition of one of our closest intergalactic neighbours, the Large Magellanic Cloud

Object:  LMC
Scope:  100mm f/5 achromatic refractor
Gear:  30mm 82˚ eyepiece (17X, 5˚ TFOV), broad band nebula filter and OIII + Hbeta hybrid filter
Location:  Blackheath, NSW, Australia
Date:  over three nights spread out over a year
Media:  White soft pastel, charcoal and white ink on black card (510mm X 635mm)
Duration:  9 hours at the eyepiece, plus four more hours tidying and finishing off at home.

Close up photo of the bar and Tarantula Nebula area showing the fainter machine-gunned stars that give the sketch the necessary lift and life seen through the eyepiece.

A final revelation came to me about the LMC while I was examining a photo of it by Marco Lorenzi.  A fantastic resource about the Magellanic Clouds is the brilliant website Clouds of Magellan:

It contains very detailed charts of these galaxies, and offers other resources such as links and even sketches of the Clouds and of objects contained within.

The LMC is classed as a dwarf barred spiral galaxy.  The bar is very conspicuous when viewing it naked eye from a dark site.  The arms are however not noticeable, instead we see these as lobes on either side of the bar.  Even the majority of photographs fail to capture the structure of the arms, instead the over processing of the photograph washes out any trace.  Yet I noticed something very special about Marco’s photo when I was comparing it to my sketch.  The arms of the LMC are actually visible in both Marco’s photo AND my sketch!

What is additionally revealed here is that the arms are not perfectly symmetrical, as would be expected, because of the significant influence of the gravitational tidal pull of the Milky Way on the LMC.

Yes, there is a magnificent barred spiral galaxy right over our heads, with two sweeping arms that wrap themselves around the whole structure.  Yet, while most of us may know of the spiral classification of the LMC, very few of us are actually aware that of its true magnificent structure, mainly because of over processed photographs, and of very few sketches of the whole galaxy.  Marco’s photo is orientated in the same direction of rotation as we see the LMC directly overhead.  The LMC is rotating in a clockwise direction when you view it naked eye.  Due to the left-to-right flip of the image with a refractor, the LMC in my sketch it rotating anti-clockwise.

You will find Parts I and II of this project in the links below:

This sketch has been one big undertaking.  From the start I was aware I had to do a lot of prep work to get to terms with the size and complexity of the LMC.  From a new sketching rig to accommodate the larger sheet, to the provision of a dew control system (if initially only experimental, but ultimately successful), and the need to adopt a different colour of illumination.  Then there were the technical challenges out in the field beside the eyepiece and the challenges crappy weather posed.  Finally the revelation of the true whole appearance of the LMC above our heads.

I sincerely hope that this sketch, and my experiences that came with it, serve to INSPIRE you, not intimidate.  I hope to inspire you to pick up a pencil.  Inspire you to not be shy about tackling the seemingly impossible.  And to inspire you to challenge yourself and explore different ways of thinking not only about sketching, but of how we go about doing our astro thing in the dark.

Clear skies and sharp pencils,

Alex Massey.

Thursday, 14 December 2017

New dobbie mount for an existing telescope.

Hi all,

With the horrid run of astro weather we have had here in Sydney, I've had to keep myself busy with other astro projects to keep my hands occupied.  So, it became the perfect opportunity to revamp a flawed little scope, and transform it into a brilliant performer!

I’ve had this 130mm Celestron Astromaster scope for a little while.  The single biggest problem with it is the poor equatorial mount it comes with.  The mount is too wobbly, and really more of a pain in the neck than what it offers.  And for beginners, this mount is the single biggest frustration that leads to this and similar scopes being put away and never used again.

The finder bracket on this scope had also broken off.  I am not too sorry about this as the original finder it came with was rubbish too.  Too close set to the tube made using it difficult, and its design is not easy to use.

So, the solution to this scope to give it a new lease on life is to ditch the eq mount and make a new table top dobbie mount for it, and install a better red dot finder to it.

I went to town on this little scope!  I had some fine materials left over from some other DIY projects, so I was able to use the following stuffs:

·      *   15mm marine grade plywood
·      *  Ebony Star laminate
·      *   Teflon bearing pads
·      *   Marine grade varnish
·      *   Stainless steel azimuth pivot bolt and washers
·      *   And a brand new 20mm red dot finder on a dovetail block.

Many dobbie mounts, including table top designs, do not have a balanced Optical Tube Assembly (OTA).  This means that if you switch between a wee little eyepiece to a very heavy eyepiece, the tube become top heavy or tail heavy when you switch back.  So these mount have a friction mechanism by which the altitude bearing is tightened, and there by making action of the altitude bearing stiffer so the tube does not drop under a heavy load.  Biggest problem with this being the quality of the action of raising and dropping the scope not only becomes harder/stiffer, but it makes tracking a target at high magnification as the action becomes jerky and very difficult to control.

Not with this little scope!

I designed the mount without any friction mechanism, but the OTA is perfectly balanced and the mount allows for the OTA to be loaded with any size of eyepiece, and the scope does not drop or rise – it stays put and the quality of the action not only remains exactly the same all the time, but it is silky smooth ALL the time!

This little scope now is a red hot, stable and very user friendly instrument.  I can swap eyepieces and the tube does not shift, even with no eyepiece in the focuser.  I can more easily locate targets because of the higher set red dot finder, and I can easily keep track of targets no matter the magnification I am using!