Tasco Starguide 114 mm - tracking issue
Posted 12 December 2010 - 05:27 AM
First post here . I am a total beginner in astrophotography and I am currently using a Tasco Starguide 114mm. I read all I could find on how to properly align my telescope on the web, and I finally managed to get the "Go to" working fine. (even though the first 2 stars won't be found initially, I would have to move the scope quite a lot manually to point to Sirius and Canopus)
My problem is, when I try a 30 sec exposition to shoot Orion's nebula, the tracking will vary from average to really bad without changing any settings from one pic to another.
I was thinking about a motors issue, or the batteries going down.
Is there something obvious I am missing here?
Thanks for your help!!
Posted 12 December 2010 - 05:56 AM
First post here . I am a total beginner in astrophotography and I am currently using a Tasco Starguide 114mm ...
My problem is, when I try a 30 sec exposure to shoot Orion's nebula, the tracking will vary from average to really bad without changing any settings from one pic to another.
Sorry to tell you this, but your telescope cannot be expected to track accurately enough for 30-second exposures -- that's why it's so cheap.
A bare-bones telescope suitable for astrophotography would cost at least $700 if you shopped really carefully. And even then you would have to struggle to overcome its shortcomings.
Easy-to-use astrophoto setups start at around $2,000.
Posted 12 December 2010 - 12:45 PM
Well, you're in good hands with Tony.
Think about what an astrophotography mount needs to do: Rotate a telescope at a rate of one revolution per day around one axis while supressing vibrations and holding the other axis absolutely steady so that light from a given star consistently hits the same pixel on your chip or the same spot on your film. The tolerances are very tight - a quarter of a percent error in that one revolution per day would give you about an arcsecond of trailing in your 30 second exposures - while the load capacity is substantial.
It amazes me every time I think about it. It isn't surprising that such a piece of machinery would weight a lot and cost a lot of money. There are some great engineers and machinists standing behind a good astrophotography mount, and they have to get paid.
Posted 12 December 2010 - 01:56 PM
Welcome to CloudyNights. Your Starguide mount is best for visual use and was never intended for astrophotography. However, there is nothing wrong with trying to do some AP with it ... just don't expect great results ... as you've already seen.
Try taking dozens of very short exposures ... around 10 seconds, or to the point you don't get star trails ... and stack them to get a final image. You'll probably get some field rotation ... stars at the corners become short arcs ... but that can be fixed with the proper stacking software. One of the greatest weak points in this mount ... other than the cheap plastic gears ... is the tripod. Make sure the legs are "in" completely and everything is tightened up. Also it's not a good idea to run this mount on the battery pack ... hook-up an external power source.
Unfortunately, astrophotography calls for expensive mounts with expensive, precision machined gears. The more you spend on a good mount, the easier it becomes to get good astro-photos with the least amount of frustration. The Starguide mount puts you at the bottom rung of the ladder with the greatest amount of frustration and the least chance of success. That said, there's really no reason not to go out and have some fun by experimenting with AP ... just don't get set your expectations very high and don't blame me if you get "hooked" and run out to spend $2000 on a new mount!
Posted 12 December 2010 - 02:55 PM
Yeah I know I won't be able to take great pictures, I was just wondering if there was any way to improve my mount's performances.
What software do you guys prefer to stack photos?
Here is attached my modest Orion shot
Posted 12 December 2010 - 05:34 PM
and here is Jupiter with same gear and a bit of Photoshop treatment. I've seen much better results with webcam though
Posted 21 April 2011 - 03:58 PM
I bought a power adapter and a small level to make sure I do the alignment as best as I can and that the power is not a problem.
The Go to worked fine, each stars were centred but then again, as soon as I tried shooting 30sec exposure photos I could see trails.
Could it come from the weight of the camera (nikon 40d) which is plugged where the eyepiece goes?
I am just starting to loose faith in my telescope tracking abilities
Posted 22 April 2011 - 12:56 PM
30 second photos of objects located near the celestial equator will always show trailing. You should try making a series of exposures starting at 5 seconds and see how long an exposure you can take before the star trails become objectionable. Don't be surprised if its around 10 seconds.
You can take multiple images and, when you combine them, apply translation and rotation to the images to get them aligned.
You can improve the tracking of your mount by making a wedge for it. If you tip the mount so that the azimuth gear follows the celestial equator; you will have "converted" the mount to an equatorial mount. Now, you can track an object using a single motor, the azimuth drive, which will, in theory, allow longer exposures. Unfortunately, taking long exposures requires either perfect gears (way too expensive) or active guiding, which your mount doesn't support. Using a wedge will also limit your view of the sky because you won't be able to image much South of the celestial equator.
You should be able to image the moon, bright clusters, and possibly the brightest nebula and galaxies. All of these can be imaged with a DSLR using short exposures, ranging from less than a second to 5-10 seconds. Planetary imaging requires long focal lengths to get a reasonably sized image. Webcams are usually used for planetary work because they take thousands of frames, allowing the few taken when the atmosphere is steady to be combined to make a good image.
Posted 22 April 2011 - 04:24 PM
Posted 22 April 2011 - 09:22 PM
Eric, cheers! yeah I have read all I could on this website and followed all alignment advices and it improved the Goto by a lot but not so much the tracking. But they say it is a different algorythm for each, so that may be why.
thanks guys for you help, much appreciated!