12 replies to this topic

[BlueMoon]

Howdy folks, I've been kicking around the idea of purchasing a Vixen AP mount configured for doing only AP. No goto, no dual axis, just RA. Tracked, not guided. I'm using a Askar ACL200 and ZWO ASI183MM/MC (I have both cameras) doing principally wide-field from 200-400mm f/l. While I admire the Vixen brand, dropping almost $1800 kitted up like this: https://astrotelesco...TVpWFlSlglnNylc is giving me pause.

 

Would like to hear from anyone using the Vixen AP mount in this configuration. Thanks and cheers.

[TopherTheME]

I don't have the AP photo guider but I do have the new version of the Polarie U. I find it to be excellent in that it's very sturdy and tracks very well with a high payload.

I did cross shop the AP unit but couldn't justify the very high price when the Polarie can be had for ~$300, fits in my camera bag, and handles my full frame camera and very heavy voigtlander lenses just fine.

[BlueMoon]

 

... handles my full frame camera and very heavy voigtlander lenses just fine.

I have an MSM Nomad rated for 7.7 lbs payload and I usually follow the 1/2 to 2/3 weight rule. Right now I'm at 4 lbs. Out of curiosity, what would you estimate the weight to be for your gear? Cheers.

Edited by BlueMoon, 11 January 2025 - 09:56 AM.

[whwang]

I once had a Vixen AP, and used it for unguided imaging with 50mm and 85mm lenses.  Unfortunately, its periodic error is too large for 85mm.  50mm is fine.  There is a possibility that I got a particularly bad copy.  But even if that true and if you get a good copy, I believe unguided imaging with a 200mm focal length will be quite frustrating.

[BlueMoon]

 

Unfortunately, its periodic error is too large for 85mm.

Ah, thanks. I'm trying to avoid the whole "guiding" mess and this is good to know. I may end up with an iOptron SkyGuider pro again after all. Cheers.

[whwang]

Ah, thanks. I'm trying to avoid the whole "guiding" mess and this is good to know. I may end up with an iOptron SkyGuider pro again after all. Cheers.

Question then becomes whether the iOptron one is good enough.  Do other people use it unguided?

[BlueMoon]

Question then becomes whether the iOptron one is good enough.  Do other people use it unguided?

I owned an SGP a few years back and it worked pretty well for me unguided up to 135mm. I'm fairly sure others use it as well for unguided low mag imaging. With a new project I'm going to be imaging at 200-400mm f/4 to f/8 which is new territory to me. I'm trying to avoid PHD2/guide cam, etc. My ZWO cameras have an ST-4 port as does the SGP so I may try a simple camera to ST-4 port direct connection. Cheers.

[BlueMoon]

Shifting mental gears on this. I'm not really finding what I want in traditional mounts. After some further reading, looks like I might bite the bullet and go after a strain wave mount with RPEC capabilities. It's not the cost (I'm not rich or anything). I just want to get it right the first time.

 

Roger Clark has some very good insights as well: https://clarkvision....racking.mounts/ The section on Periodic Errors was informative. Cheers.

[TopherTheME]

If you want imaging at 400mm without any guiding then I think your only solutions are a premium mount or a mount with encoders. I doubt the Vixen AP will deliver the performance you're after.

[BlueMoon]

For those who might be reading through this thread, my rationale:

 

My goal: simple, uncomplicated wide-field AP. Tracking only, no guiding, no extra gear, no software, no go-to, no "involved" setup or tear-downs. Level and PA - done. I've read through far too many posts here on CN and other sites from folks who appear to spend more time solving various problems than doing actual imaging. At 68, my time is becoming more precious to me in achieving some personal goals, like enjoyable AP. <smile>

 

I've been giving this some careful thought. I'm using an Askar ACL200 200mm f/4 and either ZWO ASI183MC or Canon SL3 DLSR cameras. After running some numbers and simple simulations in Stellarvue I've decided that I won't image at 400mm f/8 as I mentioned in my first post. The ACL200 at 200mm frames most of the popular wide-field targets just fine. I can frame either the Pleiades or Andromeda in the FoV of either camera for example. In simulation, I get 2.8"/px resolution (Bin 1) with the 183MC and 3.8"/px resolution with the SL3. Both afford adequate resolution error I believe to not have to worry about the periodic error of the mount. At some point I'll do some empirical testing to measure the PE.

 

The camera/lens is 5 lbs (2.26kg) max and the Photo Guider is rated for 13.2 lbs (6 kg). I'm well within the 1/2 to 2/3 weight "rule". The camera/lens is a short assembly of 11.5" (292mm) so there doesn't seem to be any worries about meridian flip to avoid hitting the mount. If I'm wrong, a short extension to the tripod will suffice to solve it.

 

Dropping around $1800.00US (at time of this posting) is a little tough but heck, if it does what I want, buy once, cry once. Cheers.

Edited by BlueMoon, 17 January 2025 - 02:09 PM.

[TopherTheME]

BlueMoon, I very much understand where you're coming from. Please let us know how it goes!

[whwang]

I am 100% with you on the enjoyable argument, especially for mobile imaging.  Avoiding guiding with a 200mm lens is possible, but quite challenging for a $1800 budget.  To do unguided tracking with AP, you very likely will need to use short subs to avoid trailing.  This is less optimal in terms of sensitivity, especially if you image at a dark site, but this is nevertheless a solution.

[BlueMoon]

 

To do unguided tracking with AP, you very likely will need to use short subs to avoid trailing.  This is less optimal in terms of sensitivity, especially if you image at a dark site, but this is nevertheless a solution.

Fortunately, my imaging habit has been to do short subs. I normally shoot 500 or more generally between 20 - 30 secs. Living in a Bortle 3 gives me a bit of a reprieve from LP.