Astrotrac & polar alignment camera.

[webby90 (Luke)]

Hi,

New to the forum & the hobby. I previously had a cheap EQ mount with RA drive and managed to get a few decent pictures for the setup, however, the motor gave way and the mount basically started to fall apart.

As a result i ended up buying the astrotrac, and haven't been very successful (i.e. really struggling with the polarscope and alignment - even after collimation - i just don't think my eyes are good enough with the scope.)

So i'm looking at using a CCD + small guide scope (ideally a 30mm - so it fits in the polarscope mount) and utilising a program like sharpcap to help with the polar alignment.

my question (after the long winded explanation) is what sort of camera is best for the lowest outlay. everything i can find online is all about using the cameras for guiding or solar/DSO imaging which isn't necessarily applicable. (i.e. don't need the best quality - just sensitive enough to detect the stars around the pole.)

My budget is basically trying to mimic the polemaster without the cost.

[sil (Steve)]

The polemaster i think IS what you want. Everything you said points to that. Astronomy is an expensive hobby if you want things to work, if you want the free ride you get nothing

[glend (Glen)]

No one 'needs' Polemaster. Polemaster came along at a time before Sharpcap's PA tool and is (Polemaster) built as a vehicle to sell their camera. With Sharpcap you can use virtually any webcam that will fit into a 1.25" eyepiece tube. A cheap webcam can work, but looking to the future, an ASI camera might be a good investment simply because of the flexibility it gives for many uses: guide camera, video camera, long exposure subs, and PA tool as well. Have a look at the ZWO website, or browse through the ZWO section of Bintel's website to get a view of what is available:

https://www.bintel.com.au/product-ca...g/zwo-cameras/

For what you want, at this stage, you do not need a cooled camera, so something like an ASI120 might be fine.
I am sure you will get all sorts of opinions here, and with the large Polemaster user base out there, they will encourage you to join them, but imho as a tool it is a bad investment given the Sharpcap tool availability now.

Btw, you do not need a guide scope to use Sharpcap PA, your camera can simply plug into the focuser of your scope, provided your scope can provide a 2 degree field of view it will be fine.

[webby90 (Luke)]

Nowhere did I say I wanted a free ride, but by the same token why would I spend the money on the pole master which only has a single purpose? Buying a guide scope and entry level CCD should be at least slightly cheaper and has the added benefit of other uses down the track should I wish to start guiding.

So while I get your response, it doesn't address the question of whether these entry level cameras (like the zwo asi034 ) are sensitive enough to see the stars around the pole.

[webby90 (Luke)]

Hi Glen,

Thanks for the info, that was my thought exactly. I have a look at the Asi120. Is the sensitivity significantly better over the 034 if like you say a webcam might be good enough to start?

[kens (Ken)]

What is your imaging camera? Any reason why you can't use that with Sharpcap?

[webby90 (Luke)]

Ahh i didn't explain that bit, sorry Ken. At the moment i'm simply using a DSLR with a range of different length lenses (so not a scope)- i could be wrong but i don't believe DSLR's are supported by sharcap - and there isn't a simple way to accurately rotate the camera around the RA axis with the DSLR attachments.

[webby90 (Luke)]

So i have found a solution to my own problem and thought i should post it here in case anyone else happens upon a similar issue.

So long story short i can do exactly what i want without having to purchase anything else and using free software.

The key is having a ball head for the camera that can be rotated without unlocking the actual ball. this allows the DSLR on the Astrotrac to rotate around the RA axis of the astrotrac.

from there it's simply a matter of downloading and install themos PhotoPolarAlign program (if you search iceinspace you'll find the topic with the required links and info).

The software is a bit more fiddly then the live view mode for polemaster, but i was able to get a decent alignment from light polluted skies when i couldn't see anything through the poalrscope.

very early stages but was able to get 2.5 minute exposure with an 85mm lens on the first go without trying to get the PA spot on (was late and i wanted to sleep).