Nadnoraa

One thing going for me is that I'm not autoguiding so PE dithers the images and the ghost moves with repect to the stars and gets reduced by averaging, basically treated like noise. The ghost in this stack of 950 x 20 sec is in the lower right corner. It is pretty amazing that this level of detail can be pulled from the sky using a cheap scope in a class 8 bortle zone.

I found this on the iceinspace.com and cloudy nights message boards so there may be hope for me yet.... the Achilles heal of any Schmidt is internal reflections. Basically the light that bounces off the CCD (or at least a portion of it) will be collimated by the primary, returning up the tube assembly until it hits the Schmidt plate. A portion of that light will be reflected by the front and back surfaces of the corrector back down to the primary which refocuses this light to form ghost images on the CCD. and this on cloudy nights Hello. About a year ago, I posted a question regarding weird blue internal reflections (Schmidt ghost)in images including bright stars, taken by my Schmidt Newt (Meade SN-10) and SCT (Celestron C8). At the time, the only solutions suggested were (1)image processing, (2)*very* careful collimation, and (3) just live with it. Recently, I purchased one of the Baader's fringe-killer filters. This filter seems to greatly reduce the schmidt ghost with a minimal loss of blue light in the image. I have done some comparison tests and would like to report the results here. The white balance frames used for the shots had the exactly same exposure time. I also tried Veil nebula and Altanik & Horsehead and the results were the same (no blue, "UFO-shaped" ghost). Because the fringe-killer filter is inexpensive (less than $90 for a 2" filter), this seems to be a must have item for SN and SCT owners who want to image moon/planets/DSOs incl bright stars.

can you suggest one? The only thing in the imaging train is a optolong cls-ccd filter but I get the same reflection without it.

Well here is my update. Covering the viewfinder did not help. Using a smaller prime focus adapter did not help. Switching cameras did not help but gave insight to the problem. I switched from my full spectrum modded canon T5 to a Meade LPI-G camera that I use for autoguiding and the refection was still there however it's geometry changed. The sensor in the LPI is more square and the one in the canon is more rectangular and the reflections show that. I'm kinda surprised that no one else ,with the sn-8, has had this problem and posted it. So I guess there is nothing that can be done to defeat this nussance. I also collected about 2.6 more hours on M45 and stacked it with the previous nights data for a total of 5.3 hours of exposure....but I am still learning to process all this with Siril and PS. So thanks for the advice guys and let me know if you have any other insight based on these pictures. Dan

Ahh ....I will try this tonight thanks for the great advice. I was just sitting here brainstorming what to do next and I thought about taking the camera apart (again) and flocking the edges of the sensor or using a 1.25" prime focus adapter instead of the 2" one I'm using now to maybe reduce the diameter of the light cone, at the price of more vignetting, but the covering of the viewfinder is a no brainer. I will be back with the results.... Here is what I got last night and my feeble attempt to remove these reflections in PS before and after....this is about 750 x 20 sec exposures with a optolong cls-ccd filter and the moon not far from M45 with San Antonio's bortel scale at class 8.

There is no metal around the sensor but there is a small border on the face of the sensor that could be the culprit, but I'm guessing nothing can be done about that. I did the full spectrum mod on this myself and roughed up the sensor bezel getting all the adhesive that was holding the ir cut filters in place so if anything that should be more light absorbent. I've attached more photos showing this ghosting in relation to the position of the star and was able to get the reflection to superimpose on the star itself in the last photo. I'm not sure what to do next other than photoshop them out (not sure how to do that yet). I'm wondering if I were to misalign the primary mirror if it would go away.... more experimenting tonight....

Hello, I've had this ghosting problem for a while and though it may be some internal refection caused by a unpainted nut or something else shinning in the ota but I've eliminated all that by flocking over everything that could possibly reflect any light. Now since this refection is blue and it's shape is rectangular it makes me think that it it could be the sensor of my canon 1200D reflecting back onto the corrector plate of my schmitt newtonian. I've gone through lots of pains collimating this scope so I don't think that is the problem but now I am out of ideas. Has anyone ever seen anything like this? What is the solution(other than getting another scope)? Dan

I just wanted to chime in on this; I was battling the same issue with processing time and the one thing that made my processing time go from 6 hours down to 24 mins was Using and external SSD (samsung T7 1Tb) on my pc's USB 3.1 gen 2 port with the USB C port on the back of my pc and the USB C cable provided with the SSD. I originally tried the same port with an apple USB C cable because it was longer and I could put the drive where I wanted but the processing time was 6 hours. Previously I upgraded my memory fom 16Gb to 32Gb (no change) my processor from an i3 9th gen to an i7(no change) The USB 3.1 gen 2 can support 10Gb/s but you need to use the correct USB cable (USB C with a thick cable ie: the one that came with the SSD) Hope that helps somebody save some $$$$.