Not owner feedback, so take this with a handful of salt...
...but given the cost of the scope (in UK or Australia) plus any focuser improvements and you have to question how much more you're really going to get out of this scope over a 4" or 5" apo. I understand how the theory works, but in practice...
If you want aperture and speed, have you looked at an f/5 imaging newt? (slippery slope, I know, when you factor in coma corrector, etc)
Well Dunk, you know I have a 10" f5 imaging newt, and it weighs about the same as the MN190. Even with the Baader Coma Corrector I prefer the images and contrast of the MN190, for it's tack sharp stars and blacker sky - don't ask me why that is technically. Yes a plain 8" f5 newt will be cheaper, and field of view similiar. Mak-Newts have their devotees and I think it comes down to the fact that they are great both visually and imaging, something that an imaging newt can't match in my opinion.
Something like a SW Esprit 120 (here) is "only" 2x the price of the MN190 and head-to-head I'd be _very_ surprised if the MN could put clean dark pixels between stars where the 120 couldn't.
Speed...yeah you got me but it's a little less than an f/stop...
As for focal length, careful choice of pixel sizes and sensitivities should be able to claw that back under most sky conditions, shy of excellent nights. But when was the last time you had one of those?
I've read some comments from one user who is a very well respected imager who has a TEC140, and he said that the MN190 outperformed it, but the difference was that the TEC just worked without any faffing all the time, i.e no messing with focusers / collimation etc.
In contrast, I have had a second hand GSO 8" RC for about 2 month which hasn't had proper 1st light imaging wise, as i'm still trying to tame the beast collimaiton wise.
So there is a lot to be said for scopes that just work straight out of the box like most APO's.
I have had a reply from Ron at Moonlight to my email regarding an adaptor for the MN190 that might actually allow a Moonlight focuser to properly align. It was a fairly long reply but I am inserting here the main points Ron made:
"I think the best bet is to add slots to the CR model universal install kit for the MN190. Getting bolts in to the slots may still be accessible even with the focuser mounted on the plate, it is going to be close? So at least with the CR 2" format focuser- it should be possible to slot it, but not the big CRL model.
I would need some measurements ( hole/ slot spacing) just to confirm it. Let me know and I'll machine them."
So it appears that A: he now knows about and recognises that there is a problem with the stock install kit for the CR focuser, B: That there is not a current adaptor that is made specifically for the MN190, and C: He is prepared to modify the stock tube adaptor to allow the focuser to be moved to align but that will only work for the CR focuser and not the larger CRL.
I am considering my next step. Given that Moonlight has not done anything to address this yet, I am inclined to keep going with the stock focuser (which I don't have a problem with, other than some slop in the slide out extension tube - which is not used for imaging anyway).
I may send Ron the hole measurements from my focuser but I don't think I want to lead the development and testing of the Moonlight solution. For those that want to see the focuser slide arrangment just look back at the photos in post #19 below.
I've read some comments from one user who is a very well respected imager who has a TEC140, and he said that the MN190 outperformed it, but the difference was that the TEC just worked without any faffing all the time, i.e no messing with focusers / collimation etc.
It's all a matter of perspective. You have to consider where the respected imager images from and the average conditions and correlate that with when/where you will practice your art. TEC 140 have a less than stellar reputation for imaging (search for blue halos), pun intended.
IMO there's little to be gained from a scope that can theoretically show you more and to experience that on one or two nights a year. Most of us don't live in the desert but the more temperate coastal fringes where conditions for high resolution astro imaging are less than ideal.
I'm not trying to discourage you from the MN190 btw, as I said I'd like one myself if my circumstances were different but there's a lot to be said for ease of use, even if you need to take a few extra subs to compensate.
What you really need is a spread of scopes to test, in parallel, on a bunch of randomly selected nights through the year. Since you list your location as UK, most of those would probably be cloudy anyway
well dunk, you have unwittingly hit the nail on the head. Imaging time is very precious in the uk due to the sucky weather, so having a faster scope F5 scope Vs F7 will make quite a difference.
I'm not so much bothered about the resolution, simply having a nice flat field and decent speed is what i crave.
Glen, i dont have a MN190 so can you send your measurements to Ron at Moonlite at least to get the ball rolling.
if you dont want to, then it's fine, dont worry about it. i'll probably buy the MN190 at some point after xmas, so i can just email Ron with the measurements then.
well dunk, you have unwittingly hit the nail on the head. Imaging time is very precious in the uk due to the sucky weather, so having a faster scope F5 scope Vs F7 will make quite a difference.
I'm not so much bothered about the resolution, simply having a nice flat field and decent speed is what i crave.
Well, if opportunistic imaging is the name of the game, then yeah that extra stop can make a difference.
If the weather is that much trouble, then it's rare/doubtful you'd benefit from the theoretical resolution of larger aperture. A 5" or _even_ 4" apo should suffice. Fast 4" apos of f/5 or so are not uncommon or outrageously expensive.
Of course, what I'm suggesting is turning the traditional paradigm on its head...angular resolution is achieved by a combination of the telescope's theoretical resolving capabilities and the size of the pixels being suitably matched to discern details. So for wide field for example, relatively large fields of view can be achieved using a full frame DSLR. For smaller objects, one of the new Sony sensors with small pixels but high QE and low read noise would be a really interesting proposal
glen
The Skywatcher sale + Thanksgiving sale was too much for me. I just ordered an MN190. Two questions:
Any tips about cooling? Did you put a fan on yours?
Would you please measure the dovetail bar length? I plan to order some aluminum and make a Losmany D type dovetail befitting this beast. I'll put the Vixen bar on top and attach the guide scope to it.
Bob
glen
The Skywatcher sale + Thanksgiving sale was too much for me. I just ordered an MN190. Two questions:
Any tips about cooling? Did you put a fan on yours?
Would you please measure the dovetail bar length? I plan to order some aluminum and make a Losmany D type dovetail befitting this beast. I'll put the Vixen bar on top and attach the guide scope to it.
Bob
Hello Bob, Yes I did put a fan on mine. The back fan port is tapped for a standard 92mm fan - I used the Orion one it fits perfectly. I mounted it with nylon screws (M3 I think they were) to minimise vibration - but this has not been a problem. It's good for cool down but really it does not take long to cool down anyway. I put the scope out maybe 30 minutes prior to start and it's equalised by the end of that time. Take the focuser plug out to get airflow through the tube and setup the fan to pull air out of the tube. You can put some filter material in the focuser if your obsessive about dust getting inside. The scope is actually pretty easy to take apart and clean anyway. I don't run the fan while imaging, it has not been necessary and would not be very effective as the focuser is blocked with the camera anyway.
As the the bar length, the long Vixen dovetail is 335mm and I have the same on the top as well, this has proved to work just fine. The cast rings have a flat section (40mm) for the Vixen bar to sit on and are tapped for the screw. I don't know how you would attach a Losmandy style bar (some of which are tube curved, some flat) but you would need to attach it on the 40mm tube ring flat. I would think making a Losmandy style bar would be fairly difficult. Certainly I have never felt I needed one.
Re guidescope attachment, I hate the screw adjuster rings used on many guidescope rings, and I use a Skywatcher Guidescope Mount on my larger scopes because it is wonderful in X & Y axis control with a single knob -but it is heavy and would need the additional Puck to attach it to the top Vixen bar. I have been using a ZWO guidescope (yes with those pesky ring adjusters) mounted to the top bar with a standard camera tripod screw adjuster. It's not the optimal solution but it works and is light.
Thanks Glen
The dovetail bar is just a piece of bar stock with 30 degree tapered sides and a few holes drilled in it. Thanks for the dimension. I have a piece of 14" x 4" bar so It should be fine.
I also have the ZWO guide scope that I plan to mount to the Vixen bar.
I see from the pix that the bar has cone adjustment. I'll have to add that to mine.
Given your comments I'll wait on the fan.
Bob
Still haven't seen mine and I'm getting conflicting emails from the vender - never a good sign.
It's is actually a custom adaptor they made after he had sent them the stock focuser base - Moonlight has offered to do the same if provided with the base hole dimensions. And no I have not done that yet, with Christmas holidays looming and the need to complete my mono dslr project I won't get back to Ron until January. I will try to send him an email but he won't take action without an order for a focuser to justify it and I can't afford that just yet. If someone wants photos and measurements for a Moonlight order I can probably get that to you and you can then email Ron to get It's started.
but it's a little less than an f/stop...
