big-guy Loc: Peterborough Ontario Canada

I have a Celestron Nexstar GPS dual fork and I know I can get 20 second exposures. If I were to get a EQ wedge how much longer could the exposure time go to?

Europa Loc: West Hills, CA

I’ve never used a Non GEM mount, so I’m not certain. I’ve heard you can do some DSO work with them. I believe the issue is that you will have curvature. This may not be as much of a problem with single images, but when you stack 3-40 hours worth, it could be a problem. Hopefully someone here has some experience with your mount and can give you better info.

Edit, I have used a Dobsonian, but it’s for visual.

alberio Loc: Casa Grande AZ

The wedge makes it an equatorial mount, however the drives and periodic error in the Nextar might be the limiting factor. Most Alt/Az mounts weren't built as a photographic platform. However if you have a SCT you could invest in a Hyperstar lens and get a wider field of view and those 20-30 sec exposures would be at f2 instead of f10. Check out Starizonas web site for better info.
I'm currently waiting for my ZWO ASI294 camera to use on my Hyperstar equipped CPC1100 in ALT/AZ configuration. You will be amazed how good this works for reducing your exposure times.
That said, not many GEMs can beat the performance of a Astro Physics mount for exposures several minutes long.

big-guy Loc: Peterborough Ontario Canada

Thanks for your response, I do have an SCT and eventually will pull the plug on the Hyperstar. While I'm saving my pennies it was suggested to get the ZWO ASI120mm Mini along with ZWO Mini Guide Scope. But I wonder if I were to get that would I really need the wedge? Yes, I understand that the wedge would help but as I'm recently retired and on a fixed income I considered building my own but.....

Your thoughts?

alberio Loc: Casa Grande AZ

I'm in a similar retirement phase and it's taken me several years to finally get the gear I need.
I've known Dean at Starizona for 20+ years and he highly recommended the ASI294 color for the Hyperstar and said to use Sharp Cap to do live stacking of the images. You would be able to this without a wedge, however any help equatorialy would be a plus. I'm not using a wedge personally.
You could go on the Tucson Astronomy Facebook page to watch the last Virtual Star Party they did with a 8" Hyperstar and a Mallincam. They did use a AVX mount, but was able to get some very detailed images of faint objects. The ASI 120mm mini might be a good planetary and guide camera, however it won't give a very wide field of view.
What do you want to do with the camera?

big-guy Loc: Peterborough Ontario Canada

I also know Dean but not near as long as you. He is an excellent source for many things. I currently have a dslr (2") and a NexImage5 (1.25") for imaging. I am looking for a way to increase exposure times to acquire DSO's and it looks like the guide camera and scope would allow me up to 60 seconds. Maybe a few more seconds with a wedge but not enough to justify the cost. I am at the beginning stage of this hobby and am well aware of the idea to spend the $$ for what you need instead of buying cheap then spending more and more. So I am looking to get quality items, learn well, then upgrade. The guide scope/camera would give me many years of service and eventually add the HyperStar system. At least that's the plan for right now.

Somewhere in the future mix is a dslr camera mod and filter system but I currently do have a 1.25 filter wheel with simple colored filters and just got a 2" moon glow filter. The moon glow does help with reducing the after glow and increases contrast a little. Anyway that is where we sit right now.

alberio Loc: Casa Grande AZ

👍👍👍

JimH123 Loc: Morgan Hill, CA

With an Alt-Az type mount, the exposure time will be limited by your focal length and where you are aiming. If you were to look straight at the North Star (provided you are in the northern hemisphere), the image will revolve around the North Star resulting in stars circling around the North Star. And with long focal lengths, this will become apparent in short order.

As you look elsewhere, the movements will change. But there will always movement. We call this field rotation.

At much shorter focal lengths, such as mounting a camera with a more moderate lens, you can go for longer periods of time before field rotation can be seen. I like using a ALT-AZ mount with a camera and lens since it is easy to set up and I can do reasonable exposure times without it being a problem. And even though over a number of exposures taken, and the total rotation builds up, the stacking SW is good enough to rotate the individual images and produce a nice stack.

Adding a wedge to the Alt-Az mount can really improve the situation. But not all mounts and not all wedges are created equal. You didn't mention which model you have, but I think that the dual fork mounts are only used on the high end Alt-Az mounts, and it may work quite well. And it will more closely approximate a GEM type mount. I suspect that your exposure time will go up quite a bit. How much, I can't guess. Depending upon your focal length, it may range from some to a lot more minutes.

I happen to have a 9 1/4" Nexstar Evolution and it came with an Alt-Az mount. The mount is quite good, but I get field rotation with it. Plus, I use a focal reducer with the scope since a focal length of 2350mm at f10 is just too much to use most of the time. I use a 0.63x focal reducer that drops it to about 1480mm at f6.3 and is more reasonable to use. But I don't use the 9 1/4 SCT scope on this Alt-Az mount. Instead, it goes on my GEM mount.

But I will mount a camera and lens on the Alt-Az mount and that is a nice setup to use.

SonnyE Loc: Communist California, USA

I've always been a GEM mount fan. It just made sense to me to let the mount take me places, hold those places, and let me do what I wanted with them. (I've known some women like that... )

Alt-Az mounts are typically for observers. Sure, back before GEM mounts could guide and track, folks used them for AP, but had to do the tracking by hand.
So if it were me, I'd approach it from there. As a visual mount. Unless you want to try your hand at very slow motion control.
Folks have attached clock motors to mounts to give them a steadier drive than by hand.
But the end result has come to a GEM type where the guiding and tracking is basically a computer controlled drive system.

I used a flip box when I first started out. It allows visual in one way, then you flip the mirror up and your camera sees the FOV so you can take a picture. Orion Flip Box for Astrophotography
Basically, you adjusted it so your camera was in focus. Then adjusted the eyepiece part so your eyepiece was in focus.
Kind of a gap filler that allowed taking pictures, and doing observation, of the night skies. Crude, but effective.

But for long exposure AP, or for days and days of data collection like has become the norm for Astrophotography, a guided and controlled mount has found it's place. And they are not inexpensive.
Even doing it "Sonny Style" with a One Shot Color camera has drained my coffers. My new mount has pushed the mount alone into the $4,000 zone. But it's complete now.
I'm committed, even though my wife thinks I should be committed. She's watching me like a circling vulture.
Just be careful, Peter. This AP crapola is like a black hole. It just sucks you in.

But a great retirement sport! You get to tell your doctor of all the excersize you get lugging your stuff out and back in, in the wee hours. And it explains why you are tired all the time.
Day sleeping isn't so bad with some earplugs or cotton to dull the banging around coming from the kitchen.
And it's a lot quieter when you get the "silent treatment" for days on end.
I already have an arrow in my quiver if things get noisy.

I mean, it's the natural progressing for me. I need a prop to keep the vortex from sucking me down....
Please send me another stimulus check to stimulate me to boost the post covid19 economy.
I promise to stay home, cooped up, and to only go out in the dark.
(It's too damned hot here for an old fart to go out in the daytime.)

If the guys in the white coats show up, run out the back!