Web Cam Astrophotography

[GalacticAccident]

Hi

I've got a Celestron NexImage Web Cam on it's way, I have a CG4 Mount, and wonder if I strictly need a drive? I'm not too flush right now, so if I can do something with the web cam to keep me happy for a while, I'll hang back on this purchase.

When/if I get a drive, how much of an advantage will it be?

I've noticed that the drive available for my mount is a dual axis. Is this strictly necessary and is there a R/A only drive available for the mount? If so, where?

Also thinking of getting a polar scope, I'm aware that polaris is not quite North, being just short of a degree out. Does a polar scope account for this in any way? How much does it matter?

Cheers

Rich

[Demonperformer]

Rich

What is your telescope's focal length? The problem with no drive [as I'm sure you know] is that the object will drift out of view. With my 1500mm f/l the image size is about 6'x8', which means an object will drift across the image area in between 24 and 32 seconds. The advantage that a webcam like the Neximage is that it takes a series of short stills as a movie and you then combine them in something like Registax, which is very good at tracking the object you want, but you will lose much of the surrounding area as it drifts.

The bottom line is that the drive will enable you to take longer movies [=more frames =better processed result] of larger areas of, for example, the moon at a time.

Hope this helps.

DP

[brianb]

wonder if I strictly need a drive?

You should be able to make images of the moon & brighter planets without one but it sure does help!

Also thinking of getting a polar scope, I'm aware that polaris is not quite North, being just short of a degree out. Does a polar scope account for this in any way? How much does it matter?

Yes. For visual work (or webcamming), not very much.

[Whippy]

When/if I get a drive, how much of an advantage will it be?

I've noticed that the drive available for my mount is a dual axis. Is this strictly necessary and is there a R/A only drive available for the mount? If so, where?

I find having a driven mount is so much easier to use, it's one thing less to think about when you're fumbling about in the dark.

I think the CG4 is Celestron's equivalent of the EQ3, so this should fit onto your mount. Best check first as I'm not 100% sure: Skywatcher - Single-Axis D.C. Motor Drive for EQ3-2 .

Tony..

[red dwalf]

trouble with using a webcam is that the field of view can be small because it`s about the same as a 6mm eyepiece, so trying to get about 2 minutes of avi video means that the object will have drifted out of view by then, it will be even harder if you barlow the webcam to increase the size and f ratio of the scope. try the moon for starters until you have the cash and get to grips with the cam and software first, it can be a big learning curve !

cheers Rob

[GalacticAccident]

Thanks for all the replies. So quick too, great forum!

Telescope is a Celestron 150mm reflector (Omni XLT) and has a focal length of 750mm.

Appears the drive is worth having. Does anyone from FLO know if the single axis Skywatcher Drive for the EQ3-2 will work on the CG-4?

Apart from saving me having to twiddle with the DEC slow motion control, (even then, once an object is found I hardly use the DEC control, if all is aligned properly, it's not needed) are there any advantages to a dual axis drive I may have overlooked? Is the dual axis drive worth the extra? If so, why?

Cheers

Rich

[John]

These people might be able to help if FLO can't:

Telescopes, Binoculars, Spotter Scopes, Microscopes and Astronomy Accessories

John

[TheThing]

I use a Tal motorised mount with a single axis drive on it, a Soligor 750mm reflector and a Meade LPi webcam for imaging (just starting on this path!)

As long as you are reasonably well polar aligned, you should be able to keep the object in the FOV for long enough to take a couple of mins worth of video which should give some decent images.

If you're aiming at a bright subject (e.g. Jupiter) than the camera should be able to make minor adjustments to keep it centre to the picture itself - with the Meade LPi, you draw a box round the subject you're focusing on and it concentrates on that.