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Old 08-12-2011, 03:23 PM
swannies1983 (Dan)
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Finding faint objects without GoTo

Not sure if this is the right thread but it relates to finding objects prior to imaging.

I've now started the exciting path of imaging DSO. I successfully imaged a few of the brighter objects such as Omega Centauri, 47 Tucanae, Tarantula Nebula and the Orion Nebula. By "successfully," I mean I have taken a few subs and moved onto the next object. Only recently have I started to spend more time on the one object (see my Sculptor Galaxy example). I will get back to the other objects as time progresses.

My question relates to finding objects before imaging, particularly those invisible to the naked eye, even through a finderscope. I don't have GoTo so what is the best method of finding faint objects?

These are my current steps for imaging naked eye visible (at least through though finderscope) objects after polar alignment:
  • center a star in an eyepiece and adjust the finderscope so that the star is centred.
  • As I said, I don't have GoTo so I rely on settings circles to find objects. I set up the settings circles based on whatever star I have centred.
  • I then attach the camera and focus using a Bahtinov mask.
  • Untighten the clutches and based on co-ordinates, move the scope to the object that I plan to image.
  • Look through finderscope to see if object is centred. Generally I find that I do have to move the scope a little to centre the object.
  • Take a short exposure to make sure object is centred on the camera.
  • Once done, start imaging.
This is all well and good for objects I can see with the naked eye. I could just see the Sculptor Galaxy through the finderscope but what happens when I can't see the object?

Is it just a matter of taking a short exposure to see if the object is there?

Would a Telrad help?

Would it be best to centre the object first using an eyepiece, then attach the camera? If I do it this way, will there be a close enough star to use to focus?

Interested to hear what people do for these faint objects.
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Old 08-12-2011, 04:47 PM
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bmitchell82 (Brendan)
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I love to image dark nebula, you cant see them with the finderscope at all and only under pristiene skies can you decern the lack of stars where you think it may be with the full aperature of the 254 newt.

So i utilise the high accuracy of my goto to land me inthe right spot even with a 254mm mirror and a CCD it still requires a 20-60 second sub image just to figure out the outlay of the whole thing followed by a full length exposure to make sure i have the whole thing framed properly!

Though do remember i have polar aligned my mount to a high accuracy followed by syncing on stars to form a triangle around the object in question this generally lands me directly in the center ready to go.

As for eye balling it, all i can say is good luck.

Brendan
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Old 09-12-2011, 12:19 PM
swannies1983 (Dan)
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I guess the question is, would a Telrad help at all in my situation?
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Old 09-12-2011, 02:15 PM
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bmitchell82 (Brendan)
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simple answer No. if you cant see the object with the finder fat chance youll see it with your naked eye. You have to count on the accuracy of your setting circles, and seeing though you are using your EQ6 with the setting circles they are not accurate enough.

What happend to the Goto on your eq6 in any case?
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Old 09-12-2011, 02:20 PM
swannies1983 (Dan)
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The EQ6 was purchased secondhand back in 2006. It came with Astromeccanica motors, controlled by DA1 handcontroller, which isn't GoTo. Only the DA2 was GoTo.

Is there anyway to increase the accuracy of the setting circles?
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Old 09-12-2011, 02:23 PM
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mithrandir (Andrew)
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Quote:
Originally Posted by swannies1983 View Post
I guess the question is, would a Telrad help at all in my situation?
Like Brendan says, you need the finder as well as the Telrad. The Telrad can get you to the right area, and with software like Stellarium, CdC, and C2A you can overlay Telrad circles to see what bright objects are close by, position them correctly in the Telrad and then use the finder to center the view.

You do need to have the scope, finder and Telrad all agreeing on the same alignment. Centre a bright object in your camera, adjust the finder and the Telrad to center it too. You could use a terrestrial object like a street light a few hundred metres away to get close.

In my case, I have to get this accurate enough so the star in the finder is in the central square formed by the double cross hairs otherwise it falls off the CCD chip.
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Old 09-12-2011, 06:24 PM
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pretty much negitive unless you can fabricate new ones with a high degree of accuracy... eg you need to be in the arc minute range! if its only the hand controller that doen't have go to capabilities, ditch it go direct to the mount and get a stellarium program to drive it..... That would be the simplest way
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Old 09-12-2011, 07:05 PM
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SkyViking (Rolf)
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I always find my targets with star hopping. I don't have goto on my mount either (Losmandy G-11 without Gemini). It's what I've always done and I've gotten so used to it that it usually doesn't take more than 5-10 mins to centre on even the most obscure invisible target. If I can't see the target visually then I get as close to it as I can and star hop the last bit while looking at the CCD frames.
I use Starry Night on a laptop and work my way from star to star in the field until I'm confident I have the target centered. I like it this way, it's a great feeling when the target finally shows op on the CCD image after I've hunted it down 'manually' so to speak.
When that's said I'll probably install a goto system in the future, simply because I can then slew the mount from a remote location so I don't have to sit next to it all the time.

Last edited by SkyViking; 09-12-2011 at 07:06 PM. Reason: typo
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Old 09-12-2011, 07:11 PM
swannies1983 (Dan)
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Quote:
Originally Posted by bmitchell82 View Post
if its only the hand controller that doen't have go to capabilities, ditch it go direct to the mount and get a stellarium program to drive it..... That would be the simplest way
Unfortunately I can't connect directly to the mount. Only inputs are on the handcontroller
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Old 09-12-2011, 07:22 PM
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does it have a PC direct option under Setup?
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Old 09-12-2011, 07:24 PM
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Do you have a Iphone or Android phone? I have been playing around with Skeye on Android I use it as a digital setting circle (DSC), once calibrated correctly they are surprisingly accurate. I was able to locate objects on my 8" f6 scope with 20mm lens easily near centre. Depending on your FOV, camera and scope setup this may be enough for you to do a quick exposure to check the accuracy of your objects location. One down side to this though is the accuracy can be a bit off if there are too many metal objects such as a telescope tube etc... Making a stand out of wood that separates the OTA from the Phone is just one of the options that prevent the phone from giving inaccurate readings...

It's just another step beyond star hopping, which for many people is a lost art. If you can get yourself some good star maps, they may be enough for you to locate some of those hidden objects..

I think Wildcard innovations argo navis has an adapter for the EQ6 also, yes they do... http://www.wildcard-innovations.com...._describe.html a little more expensive than the phone option, but would give a far more accurate reading.

Good luck with it..
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Old 09-12-2011, 07:28 PM
swannies1983 (Dan)
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Yes, but there aren't any good drivers to run it using Stellarium (StellariumScope). I only have one ASCOM driver, but it's outdated and buggy. Everytime I tried using StellariumScope, it would give me an error message saying the scope had to be "unparked." The ASCOM driver has no option to unpark.

When I tried using the same ASCOM driver with Alignmaster, I would click a star and the scope would start to slew. The problem was that it wouldn't stop slewing. I had to manually stop it otherwise the scope would have crashed into the mount/ground.

This system won't work with EQMOD and it doesn't understand LX200 commands. The only way I can guide is via Shoestring.
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Old 09-12-2011, 07:42 PM
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Okay so all you really need is a program like maxim dl with the LX200 protocol and well your done?... make it happen!
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Old 10-12-2011, 06:58 AM
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Hi Dan,

Have you seen this page for GOTO control of your mount..?

http://www.bloomingstars.com/vega/so...-JDA1/english/

It's a little outdated, but it may work...
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Old 10-12-2011, 08:17 AM
swannies1983 (Dan)
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Yep that's the driver I have tried, but it's too buggy. Hasn't been updated since about 2006. I have contacted the author and he said he won't be updating it.

I do have an iPhone but skeye is only for android as far as I can tell.
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Old 10-12-2011, 04:53 PM
graphworlok (James)
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You have a mount with RA _and_ DEC control? Luxury!

I image with an EQ3, using an EOS40D and 200mm F4 lense - Only the brightest objects are visible through the finder. Many will appear after a 30 second exposure though.

Its a bit of a pain, but for imaging faint objects, i use http://www.astrometry.net/ - it will at least tell you which way to adjust the mount. Its more useful for wide field imaging though i guess. It also means you need internet access, etc etc.

Its how i managed to get pointed at sculptor:
http://182.160.128.150/Astro/Sculptor.jpg

What sort of exposure times do you manage before PE start to become an issue? Im managing 60 second exposures, with maybe 6 out of 10 being usable
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Old 11-12-2011, 08:29 AM
swannies1983 (Dan)
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Quote:
Originally Posted by graphworlok View Post
Its how i managed to get pointed at sculptor:
http://182.160.128.150/Astro/Sculptor.jpg

What sort of exposure times do you manage before PE start to become an issue? Im managing 60 second exposures, with maybe 6 out of 10 being usable
Never measured PE but I'm able to get 5min exposures with no problems at all. Here's my recent go at Sculptor http://www.iceinspace.com.au/forum/s...9&postcount=13
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