Digital setting circles

[bearkite]

Mark... Nice description of life with Sky Commander.

I've been living with one for several years now and I too suffered from "sluggishness" during cold observing sessions. The problem is that if you don't run 12VDC to power the setting circles (which it sounds like you are) the display heater doesn't run and you will definitely suffer from sluggish display response in cold weather. As it turned out, my problem was that I had a poor connection to my 12V bus. It was a plug configuration that was coming loose during sessions. And when it got cold it got so bad I was putting hand warmers on the display face to make it somewhat useable. I've since permanently attached the power for the DSC to the 12V bus. I no longer have the problem with sluggish display. If it's "stupid cold" (below 10*F) it slows down a bit. But nowhere near as bad as when running on the internal 9VDC supply (no display heater running). Have had no problems in more civilized temps (below freezing into the teens). Mark... If you're suffering from a sluggish Sky Commander with 12V plugged in, you may want to check that connection.

As for the limited catalog space. This was actually an issue that got me thinking about switching. But after looking at Argo Navis I discovered they too suffered from limited catalog space. They don't have complete UGC and PGC catalogs. For that matter, sky commander gives you more flexibility in which catalogs are loaded than Argo. The problem is that you're dealing with only 512kb of space and that's not much. I played around with loading different configurations of catalogs and was never really satisfied. Have since gone back to the default catalog set and will either star hop or key in RA and Dec if feeling particularly lazy ;-) . The Nexus DSCs are probably going to be the "cure" for those of us looking to have our scopes do go-to's to really obscure stuff without star hopping or manually entering coordinates.

Ivan... Personally haven't seen much of a difference between ground conditions. But, I haven't really been paying much attention to that variable. I do know that some nights are better than others when it comes to pointing accuracy. Am going to have to start paying attention to my ground conditions to see if that's making a difference. Could be...

[akarsh]

Hi

My earlier observing buddy, John Tatarchuk, happened to have an Argo Navis on his 25". Turns out that when looking for those faint galaxy clusters, he had to inevitably star-hop and the thing, for some reason, kept losing alignment. So it worked well for NGC, but for the Abell clusters he was really after, he almost always had to star-hop anyway.

On the question of resolution, someone on CN pointed out these capacitive encoders AMT-102 from CUI Inc. They are available from Digi-Key corporation for those in the US. These encoders seem to have better resolution than most of the commonly used rotary encoders. I'm not sure if the Argo Navis can handle these as though they were a drop-in replacement to the "usual" encoders.

Regards
Akarsh

[Don Pensack]

I use a Sky Commander on a Teeter Classic Dob.
I have some comments:
1) I enjoy the fact the database has a lot of non-NGC objects in it.
2) I enjoy putting in about 50 esoteric objects i want to find and having the DSC find them for me. You can always just move the scope until the coordinates match but since an alt-az scope doesn't move along Dec and RA lines, it can be a little frustrating.
3) I power the unit from 12V externally, not the internal 9V battery. The advantages to that are that the LCD screen is heated and never disappears, and the scope can be moved rapidly without encoder reading errors. I use 10,000 tick encoders.
4) The accuracy is greatest where small movements of the scope don't result in large positional changes. I.e., like most DSCs, the accuracy goes down a bit as you approach the zenith. Since that's "Dobson's Hole" anyway, it hasn't been an issue.
5) Inscrutably, even after using a crosshair eyepiece to align the DSC, the accuracy varies from one alignment to the next. I can align on two stars and get a poor pointing accuracy, turn the unit off and on again and align on the same two stars and get superb pointing accuracy. I have no clue what the difference is, but I've had the same problem with 3 brands of DSCs. When it's dead on, it's great--I can use a 6mm eyepiece (304X) as a finder!. When it's only pointing poorly, I have to resort to a 21mm eyepiece to find things (87X). When it's not doing well, syncing on multiple objects in a row doesn't help the accuracy. When it's pointing accurately, I don't even need to sync it because every object is near the center of the field. I've leveled the scope, even though it shouldn't be necessary, moved the scope slowly (even though it shouldn't be necessary), and hit Enter for the position within a second of centering the object. What's different from one time to the next, I have no clue. But, at a star party recently, 3 other observers noted the same thing and told me they had experienced exactly the same issues with pointing. It's my supposition that it involves momentary errors in reading the encoders, and may be encoder related, as opposed to DSC-related. I never experienced that issue with 2048 tick encoders, but I have on all higher-tick-count encoders.
6) The units available all require too much fiddling with buttons and knbs to go from object to object. I wish they had a number pad and functioned like an LX200 hand controller: hit the numbers regardless of what menu you may be on and hit enter. Instead, we have to mess with menus and up and down motion on rows of digits. DSCs are all very crude. And while the screens can be turned off, they cannot be dimmed enough for the very darkest of sites, whether Tangent or Sky Commander, or Argo Navis. The red LEDs on the Tangent boxes (JMI, Lumicon, etc.) can be dimmed the most, but still need a dimmer setting than the dimmest. They can all be dimmed with internal or external screen covers but it would be a lot easier if they simply had some dimmer settings for the screens for those of us who view under dark skies.
7) Despite all that, the ability to find objects is dramatically improved with a DSC on the scope, and I wouldn't want to not have one.

[FaithJ]

I finally got hold of an Argo Navis, while I was in Australia earlier this month. Hopefully it won't be too much of a chore installing the encoders although I need to get some extra bits for the installation.

[Don Pensack]

Faith,
You might look at JMI's website. They seem to have kits and pieces of kits to mount encoders on just about every scope that's made.

[rmollise]

The Argo Navis is fine...but for me all its features are an annoyance more than a help when I am using DSCs. Best damn unit I have ever used in every respect? Sky Commander. ;-)

[Don Pensack]

The Sky Commander has some problems (though I own and use one):
--it fades out in the cold. The answer is to power it from a 12V power supply, which heats the screen, but that isn't necessary with the other DSCs.
--the screen is too bright at minimum setting. I fixed it with some dark cellophane between the screen and the window, but that isn't necessary with other DSCs, which can be turned down to lower brightness settings.
--if you hit the wrong button, there is no easy "back" or "Escape" button, and since the buttons are not illuminated at night, it's all too easy to hit the wrong button when wearing gloves.
--the database is a little too small for any scope over 10". Or, to put it another way, thousands of objects visible in small scopes are NOT in the database, while thousands of objects that are NOT visible in small scopes ARE. This is an issue with other DSCs, and computerized scopes, too, so this complaint is not unique to the Sky Commander.

That's about it. Otherwise, I like it, and it works.

[rmollise]

--Must be a lot colder where you live. I have never, ever had to exercise the 12volt option. Not once.

--At the lower setting I find brightness just right.

--I do wish the keypad were illuminated, I get tired of having to point a red light at the keypad. But I've never got myself into something I couldn't back out of.

--If I want more, I'll hook up a computer. Most of the time the good old NGC/IC is enough, however.

;-)

[Don Pensack]

Rod,
At my high-altitude site (2550m, 8350'), it can be 0C (32F) in August. Last month was a warm 4C(~38F) near dawn. Without the 12V connection, the SC is not usable after 10pm.
I also must observe under darker skies. At low setting, I can see the screen from 200' across the parking lot. I tape over all my red LED operating lights because they hurt my eyes at night.
The problem with the NGC/IC (and the database in the SC isn't complete) is that there are literally thousands of open clusters without NGC numbers. And a ton of globulars, small bright nebulae, dark nebulae, etc. If I were doing the database for a DSC, I would start with the items visible in smaller scopes and then fill in fainter and fainter until I reached a reasonable limit (say, magnitude 17) instead of including some at that fainter limit and ignoring a lot of Mag. 5 objects.
Hooking up a computer is a guaranteed way to ruin your night vision, so I eschew the use of anything with a screen larger than the SC. As a general rule, if you can see it and read it in twilight, it's too bright for night use.

[Jim Chandler]

Hooking up a computer is a guaranteed way to ruin your night vision, so I eschew the use of anything with a screen larger than the SC. As a general rule, if you can see it and read it in twilight, it's too bright for night use.

Enter the eyepatch. At the eyepiece, cover your non-observing eye to allow it to be fully relaxed. At the laptop, shift it to cover the observing eye. After looking at a deeply red-filtered, very dim laptop for a minute or two, a blink comparison between the covered and uncovered eyes shows the obvious degradation in dark adaptation to which Don refers. The patch allows the use of the laptop without sacrificing dark adaptation.

The benefits of covering the off eye while at the eyepiece should not be ignored either. Having the off eye completely relaxed aids in concentration and ultimately allows you to see deeper. Having tracking, using a hood, using an eyepatch; each one eliminates a small but noticeable demand on your attention. Getting rid of each of these distractions incrementally improves your concentration.

Walgreen's house brand eyepatches have a nice, stiff eyecup and reasonable life expectancy for the elastic band.


Rod, is it just me, or does anyone else detect eerie overtones of the circa 2000 discussions about "real astronomers don't use DSC's" in your the-SC-is-good-enough-for-me comments? <g>

[rmollise]

SkyCommander gets 'sluggish' in very cold climate so if you are always in the ice cold I suggest avoiding this controller. It is like it's clock for the microprocessor is an 'R/C' clock and not crystal controlled. It's time of day clock of course has to be the classic 'watch crystal' so must be accurate to track but alas, I digress into geek-speak.

I've never worried about anything but azimuth and that star two isn't too low. Polaris is my Star One, always, and Procyon and Fomalhaut take up the slack the rest of the year. Polaris and a star 90-degrees plus away in azimuth and I am ready to go. As I mentioned earlier, my Sky Commander has never gotten sluggish enough in the cold to worry about, but if it does, as was also mentioned earlier, power it with 12volts and an internal heater kicks in as needed. :-)