Lunar Mystery Location

[Tommohawk]

I was trying out my modified Quattro with 5x powermate last night but difficult to get much detail with the moon being pretty much 100% full. This was the only image worth keeping TBH, but I blowed if I can figure out where it is. This rig is a bit unusual - I use the camera at prime focus with no secondary - which means I think it has one less plane of reflection than a regular Newt. Maybe not.

This region ought to be South West - but I can't see it on any atlas. Grateful for any thoughts!

Edit: Byrgius maybe?

Quattro 250 with Powermate x5 and Omegon 385C. Captured with Toupsky, 8 minute run at about 40 fps, best 5% AS!3 + Registax + PS

 

Edited February 27, 2021 by Tommohawk

[Cornelius Varley]

The crater with the ejecta rays is Byrgius A

[neil phillips]

Interesting setup. Scope sounds quite fast. But that is a excellent shot 

[Tommohawk]

21 hours ago, Cornelius Varley said:

The crater with the ejecta rays is Byrgius A

Thanks for that - somehow I studied the atlas for ages, and then about 5 mins after posting I figured it out. I used to work with low mag to start with just to plan what I was going to view/photograph and then switch to high mag. With the current setup that isnt practical - I have to start with high mag so getting oriented is problematic and a lot of the landmarks are washed out with full moon. 

17 hours ago, neil phillips said:

Interesting setup. Scope sounds quite fast. But that is a excellent shot 

Thanks Neil.

The scope is a bit of an experiment - the idea was to use a fast mirror just to keep the scope length down to minimise momentum etc, and then use the powermate to give the higher EFL. (F20, 5000m EFL) Mounting the powermate/camera assembly  on the secondary spider means there's less central obstruction - the Omegon OSC Velox 385 camera assembly is only 43mm diameter. It's based on a Flextube 250 housing a faster Quattro F4 mirror - see pic below. Long term I wanted to do the same thing but as a truss design so I could disassemble and travel with it easily.

In general it works very well, is really easy to collimate and holds collimation very well too. The big issue is focussing - I've built in a helical focuser which works well, but it really isn't possible to focus on surface detail because theres just too much image movement - I prefocus with a Bahtinov which does the job nicely.

I used this rig extensively with Mars last year, and TBH I don't think this gives quite the resoluton I was hoping for. My conclusion is that (cheap) fast mirrors suffer from aberrations such that any marginal gain from the reduced CO is lost. It would be interesting to repeat this with either a better mirror or maybe say an F5, although an F5 250mm would be about 1.5m long including the camera assy. and would probably need a bigger mount. Currently my HEQ5 just manages this with a stack of extra weights!

 

[neil phillips]

7 hours ago, Tommohawk said:

Thanks for that - somehow I studied the atlas for ages, and then about 5 mins after posting I figured it out. I used to work with low mag to start with just to plan what I was going to view/photograph and then switch to high mag. With the current setup that isnt practical - I have to start with high mag so getting oriented is problematic and a lot of the landmarks are washed out with full moon. 

Thanks Neil.

The scope is a bit of an experiment - the idea was to use a fast mirror just to keep the scope length down to minimise momentum etc, and then use the powermate to give the higher EFL. (F20, 5000m EFL) Mounting the powermate/camera assembly  on the secondary spider means there's less central obstruction - the Omegon OSC Velox 385 camera assembly is only 43mm diameter. It's based on a Flextube 250 housing a faster Quattro F4 mirror - see pic below. Long term I wanted to do the same thing but as a truss design so I could disassemble and travel with it easily.

In general it works very well, is really easy to collimate and holds collimation very well too. The big issue is focussing - I've built in a helical focuser which works well, but it really isn't possible to focus on surface detail because theres just too much image movement - I prefocus with a Bahtinov which does the job nicely.

I used this rig extensively with Mars last year, and TBH I don't think this gives quite the resoluton I was hoping for. My conclusion is that (cheap) fast mirrors suffer from aberrations such that any marginal gain from the reduced CO is lost. It would be interesting to repeat this with either a better mirror or maybe say an F5, although an F5 250mm would be about 1.5m long including the camera assy. and would probably need a bigger mount. Currently my HEQ5 just manages this with a stack of extra weights!

 

Very interesting Tom. F5 might be the way to go. A good performing primary is everything. So a quality F5 Mirror might give you what you want. I got good results with a bog standard F5 300mm SW. The NEQ6 Pleaded for mercy though. It worked better at IR and red wave lengths. The better the primary mirror the better the blue and green will likely fare though.  (red too )  But as you say its a budget and physical balance thats right for you. Just getting a Antares 1/ 30 pv secondary fitted for my Orion

1/10th wave 245mm F6.3 scope.  So thats where i am going. But if you make any changes i will certianly be watching. Would love a zambuto mirror  the wait is very long, though i think he may still be making them. John Nichol is also a craftsmen.

Edited February 28, 2021 by neil phillips

[Tommohawk]

31 minutes ago, neil phillips said:

Very interesting Tom. F5 might be the way to go. A good performing primary is everything. So a quality F5 Mirror might give you what you want. I got good results with a bog standard F5 300mm SW. The NEQ6 Pleaded for mercy though. It worked better at IR and red wave lengths. The better the primary mirror the better the blue and green will likely fare though.  (red too )  But as you say its a budget and physical balance thats right for you. Just getting a Antares 1/ 30 pv secondary fitted for my Orion

1/10th wave 245mm F6.3 scope.  So thats where i am going. But if you make any changes i will certianly be watching. Would love a zambuto mirror  the wait is very long, though i think he may still be making them. John Nichol is also a craftsmen.

I seem to remember you did some cracking planetary images with your Orion so will be interesting to see if you can squeeze even more out of it with your 1/30 PV secondary - watch this space as they say! Interesting to know that your primary is 1/10 wave, must make all the difference

I reckon a quality 300mm F5 in a purpose built truss frame would suit me well, but I don't have my own workshop so have to use a bit of ingenuity and adapt stuff. The flextube idea worked well because it allowed me to coarse tune the scope length, but its a heavy scope and I couldn't do the same with a 300mm. 

[CraigT82]

That's an absolute belter of an image! Really nicely processed too. We don't see these features often purely because not many people bother with rhe full moon. Thanks for posting 👍

P.s. I love that scope! 

[Tommohawk]

Thanks Craig, too kind!

[neil phillips]

1 hour ago, Tommohawk said:

I seem to remember you did some cracking planetary images with your Orion so will be interesting to see if you can squeeze even more out of it with your 1/30 PV secondary - watch this space as they say! Interesting to know that your primary is 1/10 wave, must make all the difference

I reckon a quality 300mm F5 in a purpose built truss frame would suit me well, but I don't have my own workshop so have to use a bit of ingenuity and adapt stuff. The flextube idea worked well because it allowed me to coarse tune the scope length, but its a heavy scope and I couldn't do the same with a 300mm. 

One thing i know for sure. Regardless what people say about figures  of mirrors. A good set of optics will betray themselves over a period of time, purely imaging. In the end the best optics are more consistent. And do show in consistently good images, with good collimation and cool down of course. Seeing is a different matter

Theres good and bad mirrors and everything in between Despite pv claims