alignment woes (CGEM)

[corpusse]

I'm still having a great deal of trouble aligning my mount for photography. Sometimes I get it real good, as evident by my last m42 photo posted a few threads down. Today I can't even take 10 second shots without star trails..

I've tried to polar align in the menu of the nexstar. Last time it seemed to work okay but it always puts me further from the object and makes it really hard to center without changing back to eyepiece and then there's getting the focus right again..

Finally whenever I have perfect visual go to, where the object is centered at the push of a button it's always terrible tracking for photos.

I was all set to go and try and image m31 but it's already behind my house and the scope is way too heavy to bring in the back in this cold. I'm going to try and realign again later tonight...

[admin]

Hey there,
I didn't realize you got a CGEM! nice stuff congrats!

Do you have a polar scope?

Also have you tried using a digital angle gauge or similar like rope/protractor and a compass to figure out the latitude setting/direction you should point your mount?

I would also do a 3-star alignment to get rid of cone-error and make sure the scope is tracking well. With the CGEM you should easily get 45 second shots without trailing. If not, and you don't want to waste any more time you can jump ahead and learn drift alignment which allows even 1 minute shots if you do it accurately and can be used as an accurate polar-alignment as well.

If you can setup a permanent or at least roll to observatory you will save on polar aligning every time, that is why it also pays to get a GPS eventually because it keeps your scope tracked to exact time so you never have to polar align/align stars again and just get to imaging/viewing straight away. That is what I wish to accomplish eventually anyways,
clear skies!

[Ghostryderflyby]

Corpusse, in the prior thread about this you never mentioned how you are entering your GPS coordinates. Did you pick a near city from the list of alignment cities, or enter your actual coordinates? If you used a city close to you, the coordinates could be off enough from your actual coordinates to induce error into the mount tracking. I recommend using a GPS and obtaining your actual coordinates for best accuracy, and as Gus said, at least a 3 star alignment. (I have found 5 stars makes it literally error free in both finding and tracking and always do 5).

As mentioned in the previous thread, I use my actual GPS coordinates and the time from the government time website. That gives the mount the most accurate information to work with, and I've tracked an object for 45 minutes without it slipping in the FOV. Granted the longest exposure I've done is 15 seconds, but you said you were getting slip within 10 seconds and I've not seen even a hint of slip in my 15 second exposures.

The only other possibility I can think of aside from the possible firmware or motor control problems mentioned in the other post, is imprecise alignment or possibly pushing the mount slightly off target changing EP's, inducing subsequent tracking errors. Not saying you are doing either of those, again just covering our bases.

Hope you get it figured out. That's got to be frustrating. I can tell you from experience though if you get it sorted out, the CGEM is a terrific mount with stellar (heh ) tracking capabilities.

[Dublin sky watch]

I am sorry that I cant help much here. I can feel your frustrations in your post. I would say this though. I too have problems with my scope when tracking and I only have altazimuth mount. However I find going inside for a cup of coffee helps me calm down!!

I have a scope that costs me the guts of €4000 and a camera with accessories that cost over €3500...so I cant really kick anything in front of me. I have to be patient with the equipment and with how I use the equipment. I reread everything twice and probably a third time as well. I recently bought a wedge for my scope, so I shall have great fun trying to polar allign this monster correctly.

So it wil come good in the end, just take your time with it and the rewards will flow.
Cler skies to you.

[corpusse]

I'm using my iPhone for location. Maybe the compass isn't entirely accurate. I will double check with car gps next time. I need an eyepiece with crosshairs to try drift alignment. That is my next step. I have been able to do 45 second exposures but other nights only 10.

[jpalmer]

its going to be differant from here inthe uk .

with mu eq5 the pola scope has a cross hair with a circle on the circle is a very small circle i do beleive that im ment to keep the noth star inthat small circle . so far ive managed nearly 3mins before stars have tails . and some nights i cant manage that so pola alignment has to be spot on.

many thanks
jason

[Ghostryderflyby]

Corpusse,

Based on a tip from Klaatu and Austin, I went digging around for information on drift aligning the CGEM. I found this article that might help with the problem you're having with star trailing.

Hope it helps and good luck!