Hello,  I wanted to ask what the recommended Backfocus for my 8" f/4 scope (native) with the ASA 0.73x reducer is - I don't find documentation for this on any of the pdfs/drawings. Doesn't it perfrom well with a 8" or what's the reasoning behind this?  I can get down to an absolute minimum of 66.3mm which I fear is too much (basing on numbers for a f/3.8 system and different mirror sizes). Filters would add 0.7mm to the BF of the reducer.  Any help is much appreciated!    Best,  Tim ..read more

Hello, I have a 12.5" f4.1 (1300mm) Native Newt that I am trying to setup my 8 year old ASA 2" .73 reducer corrector so it becomes a 12.5" f3 (950mm).  It will be used with a QHY268m camera who's diagonal measures 28.3 mm. I believe that the right back focus is 65.5mm but I wanted to be sure and also see if there are any variances to get the best image quality. Thanks in advance! Chris ..read more

This is a transfered topic from the ASA Yahoo Group.     Posted By: doug_landmann Thu Apr 18, 2013 5:27 pm Why is it that get two different answers for the thickness of the adapter required if I use the ASA calculator or and if I take the optical backfocus number from SBIG and subtract it from the ASA backfocus requirement? ASA 10"N Wynn 3" corrector f/3.8 backfocus from Chart A = 57.29mm Which is the same number that comes up in the spreadsheet calculator for the 10N with Wynn 3"corrector at f/3.8 Using the calculator and accepting the 1mm glass thickness over the CCD sensor and ..read more

I have this ASA 3" Wynne corrector for more than 10 years and in the last few years I noticed that the coatings on one lense surface is basically failed (blue channel suffers the most). Image 1 Image 2 The images are of the lense on the telescope side (the lense that bulges out). I'm trying to get some information if this can be recoated (somehow strip the coatings by repolishing or chemically), but I get no answers from ASA, which is where I bought the thing. I just want an answer if this can be salvaged, so I can move on and buy another or get this fixed. Thanks ..read more

I want to sell my ASA accessories: ASA 1.8x barlow for newton + original adapter for this barlow Selling price on the web = ASA 1.8x barlow = 1098 euros + 200 euros ASA adapter = 1298 euros. My new price is 600 euros If you are interested, please contact me. astrojurista@gmail.com   My photo with this ASA 1.8x barlow https://astrofotky.cz/gallery.php?show=Peter.Jurista/1518558945.jpg   Peter ..read more

Hello, I am searching for an ASA 4" field corrector for newton. If you have one  that you don't use, make me an offer. Thanks ..read more

I recently acquired the 0.77 SCT corrector via the second hand market. I know this is no longer sold but wonder if someone can help me. It is stated to have a 0.77 reduction factor, but when I fed this into my plate solving system (NINA+ASTAP) I got errors and the system eventually reported a rather longer effective focal length from my C8 SCT+ the Keller/ASA part. It corresponds to a reduction of around 0.88! So I am curious to understand what might have happened. I had previously been using a Starizona corrector with a 0.71 factor and that was confirmed by the solver. I adjusted my Backfocus ..read more

Hi. I use ASA N10 and 3" wynne corrector with QSI683wsg camera. And I use astrodon 31mm filters. and adapter made by ASA for qsi683wsg. When I took a picture with above system, there is vignetting on each corner. I wonder that where the vignetting came from. Is it just vignetting or interference of ray path with adapter?? Here I attached raw image file (R channel, 300sec exp. 2bin), please some one analysis it  Thank you for advance.   m3 -001r.fit ..read more

Goodevening. I'm italian guy, i buoght a 3" 0.73x corrector used from a austrian guy. while I was taking the measurements to make the fittings I realized that they were different from the specifications.  I have attached photos of the corrector and the pdf with the specifications of the corrector ... even the real length of the corrector is different!  have different models been made?  Thanks for your help.  Giovanni.Corr_3Zoll_Reducer.pdf ..read more

Hello,   After 2 years of use my ASA10 telescope is good for a great cleaning (The countryside brings a lot of dust, pollen. I have a hell of a lot.) I will do this in the summer to minimize the waste of time.   While browsing the documents, it is mentioned to remove the primary mirror from the telescope to use special screws. Mirror cell handles.     I do not remember seeing these screws during my purchase and I would like to know if it was possible to use something else?   Thank you in advance for your return.   Thomas ..read more