Re: [ap-ug] M33 with 92mm Stowaway, combining RGB, H-alpha, and O-III

Dale Ghent

I never did get the CFF flattener because it wasn't available when I received the CFF92, and I wanted to try to find a reducer+flattener system that had the same (or very close to the same) BFL so they could be interchangeable using the same Precise Parts adapter, with only a few shims of difference between them. But that didn't happen and all I've been using is the M63 reducer. That was perfectly fine with the 4/3 sensor in the ASI1600 I was using on it. The QHY268 pushes it just enough more that it's flaking out rapidly at the corners, as f/4.5 light cones are good at doing. I'm sure APS-C would be fine corner-to-corner on the slower f/6.9 version of the CFF92 with this reducer.

A "unicorn" solution, for me at least, would be this super reducer that can be stuffed into the rear of a 3" FTF or Nitecrawler, with a paired flattener that has the same BFL to keep framing options open without much ado when it comes to adapter configuration.

On Dec 13, 2021, at 15:42, Bill Long <bill@...> wrote:

Well this is good information. The CFF92 was the other scope I thought of for being in the game for a well corrected field. Sounds like it's not terrible with the reducer, but could be improved on.

What about the flattener? Can it cover the IMX455.

Either way, sounds like more positive data for the AP92 upgrade option for the full frame capability and the TCC.

From: <> on behalf of Dale Ghent <daleg@...>
Sent: Monday, December 13, 2021 6:13 AM
To: <>
Cc: <>
Subject: Re: [ap-gto] [ap-ug] M33 with 92mm Stowaway, combining RGB, H-alpha, and O-III

It’s something I would be interested in, and I don’t even have a Stowaway. I have a CFF 92 f/6 refractor and the M63 APM-Riccardi reducer that have been using on it is baaaaarely passable, with some leniency, when using it with my APS-C sensor. I’m using an OAG with this scope since it’s a compact travel imager, so its pick-off mirror is definitely sitting outside the corrected area in order to avoid intruding into the sensor’s fov. A larger corrected field is certainty something that I miss and would jump at the opportunity to have, even if it meant a focuser upgrade (my CFF 92 came with a 3” FTF; an improved optical design similar to the M63 format or a little larger, would be fine in my case.)

The APS-C Sony IMX571 sensor that is now in many CMOS astrocams is a fantastic sensor and is fairly accessible in terms of price, which is fueling its rise as a common sensor to see now. It’s the smaller cousin of the full-frame IMX455 which is also popular, of course. A TCC and flattener that could competently handle both would be noticed. Other makes of (mainly Chinese) refractors in the 90-110mm range also lack a competent reducer/flattener for these sensor sizes and one could find use with those.

On Dec 11, 2021, at 19:33, Roland Christen via <chris1011@...> wrote:

It's certainly possible to design and build a super sharp telecompressor for the 92 Stowaway to cover the full frame CMOS cameras with sharp round stars into the corners with no vignetting. It would require 3 things, a more exotic compressor design, a larger focuser and market for it. It would be more or less a super astrograph, rather than a small fun portable scope, plus it would cost more. Is the interest there or not, that is the question.


-----Original Message-----
From: Roland Christen via <chris1011@...>
To: <>
Sent: Sat, Dec 11, 2021 6:15 pm
Subject: Re: [ap-ug] M33 with 92mm Stowaway, combining RGB, H-alpha, and O-III

Tonight I'm shooting in very clear skies, very cold sub-freezing, but poor seeing. Moon is also nearby.


-----Original Message-----
From: Eric Weiner <weinere@...>
Sent: Sat, Dec 11, 2021 6:09 pm
Subject: Re: [ap-ug] M33 with 92mm Stowaway, combining RGB, H-alpha, and O-III

Thanks Roland. I have the 92FF as well. Just exploring my options. Focal length of 644 vs 488, a 1’x0.7’ delta. That’s worth the trouble of flats for some targets imho. Our skies in Colorado have been terrible so I haven’t had a chance to experiment with the TCC myself yet. I just got it on Monday.


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