vlaiv

Hi, yes, it's related to bayer matrix. Under ideal conditions - one would do twice sampling rate and then split matrix into RGB components where there would be twice as much G subs then R and B. Processing would then be much like mono + filters. Alternative is to do full processing at twice sampling rate and then reduce image size by factor of 2 in the end for sharpest results (many people don't do this and tend to leave their images over sampled which results in blurry looking image - I don't like it but most don't seem to mind it).

You seem to have 15x70 binoculars? That is not far away from ST80 experience. You'll be able to change magnification but only use one eye for observing. Image will be slightly brighter but not by much. It should also be sharper and depending on eyepiece used - larger AFOV.

Only issue I've found with short refractors on this mount is observing near zenith. I had ST102 and TS80 F/6 apo mounted on AZ4 and both would sort of hit the mount with focuser knobs when looking straight up. If that is concern to you - check how would 130mm tube fit that mount by using some sort of mock up (there is a chance you would not be able to look at zenith targets with wider OTA as it would hit the mount head). This image illustrates potential problem - just imagine OTA pointing straight up - it would definitively hit mount base.

Primary mirror is fixed with this model at correct distance and generous back focus is just feature of these scopes to allow for variety of attachments (2" diagonal, field flatteners and reducers, oags, filter wheels and so on).

I had the same dilemma, but image names solved it for me. Top, blurry one, ends with "Capture17_04_201423_13_08z.png" and there is mention of previous result of about 5 years ago. Bottom sharp one is titled MarsBestsofar.jpg - I figured that must be recent image we are talking about.

Just love that this has been edited

I don't see why not, Sony E-mount has 18mm of flange distance, so you need adapter that is at most 11.5mm long (optical path) and you should be fine.

It is extremely difficult to get such focused light on sensor from light leak - it needs to be focused by optical element or diffracted of an edge in the system.

I'm now getting 6932.736 Just to make sure there is no error, let's do it step by step CC: (93.25 x 93.25 - 34.25 x 34.25) x 0.96^2 = (8695.5625 - 1173.0625) * 0.96^2 = 7522.5 * 0.96^2 = 6932.736 Mak150 to CC = ~25% increase in light CC to C8 = ~25% increase in light This time it sits pretty much in between the two.

I just came across very important point for 8" CC if it is indeed stopped down to 7.3". Secondary obstruction is 68mm and primary is 186mm. That makes secondary obstruction almost 37% rather than 33%.

https://www.orionoptics.co.uk/VX/vx6-6l.html OO UK say that their VX6L weights 5kg which is 11 pounds.

I'm only mentioning it because it was on the list of possible scopes in the initial post. In my view, except for the high end ED refractor (or triplet) which is not considered both because of price and bulk, this scope will give best views of the lot. Every other design is compromise in some respect.

It's actually lighter than that - only 11.9lbs. If length is not an issue, I would still consider 6" F/8 planetary newtonian first. 1/10th wave optics and less than 25% central obstruction is bound to give views that are refractor like.

Not if you use that 60mm F/5.9 or get decent Samyang lens. I've got ASi178mcc - color cooled version and can't wait to test out newly acquired 85mm F/1.4 with it.

You probably did not notice that there is finder scope in that image as well

RC is also corrected for coma and has only astigmatism left. It has large corrected field with very small amount of curvature. It is good scientific instrument (most professional scopes are RCs) and good for imaging. Not as good for visual because central obstruction is usually much larger. It has two hyperbolic mirrors. In this particular case it is F/8 scope suited to DSO imaging. CC in this case is F/12 and central obstruction is smaller - good for visual and imaging of planets.

It should. It is about 6Kg in weight (FLO lists it at 6.3Kg while TS has it at 5.4Kg) so it is not one of the lighter scopes. Add diagonal, eyepiece and finder scope and you could easily push past 7Kg. Since it is short tube it might work without too much trouble, although I've seen just few quotes that Eq3-2 can carry 7kg and most of the time it is listed at 5kg. Maybe consider EQ5 after all as it will be much more stable platform. CC are completely corrected for spherical aberration, so are SCT and MCT. SCT can have spherical aberration because its correction depends on distance between mirrors and since they focus by moving primary mirror - there can be more or less spherical at certain focuser position. CC does not suffer from this and it should be completely free from spherical aberration. It does have some amount of coma and astigmatism and here are expressions for those: As a comparison here is coma of Newtonian telescope: D is diameter of aperture F is F/ratio of the scope. Expression for coma is the same and CC has as much coma as F/12 Newtonian - very small amount of it. In comparison, 8" F/10 SCT will have coma similar to F/6 Newtonian. All above info can be found here: https://www.telescope-optics.net/

Drawer is really not practical for planetary as one needs to change filters rapidly as not to loose any imaging time (planets rotate and one does not have very long window for imaging). This is why I linked to EFW. Maybe even regular manual filter wheel could be used, but I would not use drawers for planetary. DSO imaging is different - you don't loose much of imaging time if you spend one minute on filter change there.

I vote for this one, although, if Mak150 is too heavy - I think 6" F/8 will be as well and much bulkier.

I use baader RGB filters for DSO imaging, but I think for planetary I would go with cheapest filter set as you don't need to worry about faint reflections / halos and such. As for filter wheel - I don't have one, I use filter drawer, but I did get my eye on one of these since I'll be making permanent setup / obsy next year: https://www.firstlightoptics.com/filter-wheels/zwo-mini-electronic-filter-wheel-efw-5-x-125-or-5-x-31mm.html It's not that expensive and has positive reviews. I did not do much research but you want your EFW to be repeatable - filters always in the same position (so you can reuse flats) and there is no light leak.

You are not guiding and this is to be expected - it is combination of polar alignment error and periodic error. Every mount has it to some extent and this is the reason why people guide - to eliminate the two. Look at that line in 20 minute image. It has smooth component in one direction and it has oscillatory component in perpendicular direction. If you check your images, you'll find that smooth component is in DEC direction - that is drift due to polar alignment error. You will also find that perpendicular to that - what is causing "waves" is RA direction and cause of those waves is periodic error - which is due to fact that gears are not perfect circles. Look at the same thing happening as a movie: Either start to autoguide or check your mount manual for something called PEC - which is periodic error correction and try to see how much it will help. For better polar alignment - look at drift method.

You can usually judge bayer pattern from the image itself. There should be standard in how image is oriented and indeed FITS file format specifies data order for each axis, however there is problem of how sensor is interpreted. I think this is because someone long time ago decided that screen space is inverted, so Y axis, top pixel is 0 and positive values go down the screen. On the other hand mathematicians and scientists are used to "normal" coordinate systems where up is positive Y direction. When you read data from sensor line by line - do they form image by going up (like in math) or going down (like in computer screens)? In fact, FITS format don't care - as long as you write it the same way you read it from sensor. It is up to image processing app to interpret what it reads from FITS and shows on screen. In any case, here is top left corner of the raw image from OSC camera: This is either RG or BG pattern. This can be judged as green pixels tend to have about the same intensity and you are looking at pattern of matching intensities that go diagonally. Green also tends to be brighter than the other two (except in some camera models that have strong R, these are usually sensitive in IR for surveillance application - look at response curves and see which color has the peak). Since this is shot of the sky and there is some LP - images usually end up with red background - red will be stronger than blue. Pattern here is therefore RGGB. In any case, if you get G right from the raw image - other two can be mixed up but it does not matter, you can fix this easily in post processing by swapping red and blue channel. Problem is if you don't get green right, then you can't do this swapping because R and B end up combined and not as separate channels.

No, this is similar to perspective. What you'll be measuring is angle and objects of a different size will subtend same angle if they are at different distance. For this reason there is no way of knowing the distance if you have only angle. There are things in astronomy that can be calculated by using similar principle - like transits of bodies - using first, second, third and fourth contact you can calculate things. You can also estimate the distance to the galaxy if you know the type and angular size in the sky. Due to rotation of the earth - no, both "move" at the same rate. Due to proper motion - sure, but again that depends on speed of object. Object twice as far away moving at twice the speed will again subtend the same angle (as it will cross twice the length).

If you want to focus on lunar - sensor size plays a part - the bigger the better as you'll need to take less panels for lunar mosaics. 178 wins here. For lunar I would also consider mono over OSC as there isn't much color on the Moon. Mono will also let you do some fancy stuff better like UV photography of clouds on Venus and CH4 methane band and use of NB filters to tame the seeing. Again, 178 has 2.4um pixel size, optimum sampling rate is F/9.4 for mono and double that for color (F/18.8) 290 has 2.9um pixel size, optimum sampling rate is F/11.4 for mono and double that for color (F/22.8) 120 has 3.75um pixel size, optimum sampling rate is F/14.7 for mono and double that for color (F/29.4) I'd say you would need barlow for any color camera and ASI120 in mono. 178 and 290 in mono don't need barlow as they are close to native F/10 of the scope. ZWO is not the only game in town, QHY, Altair Astro also make cameras with same sensors. If you can, get USB3.0 laptop and camera as speed of USB 3.0 enables much higher frame rates to be achieved - means more subs captured, means better stack / better SNR.

Problem is that even small variations change things significantly. John measured primary to be 204mm and that is more in line with 8" = 203.2mm. I think we would need full specs to be able to do the math - otherwise it will always be few mm here and few mm there that change the picture. I wonder if we could devise a test that can be easily carried by someone that would solve this. I know how I would test it, but it requires a bit of gear that most people interested in this scope don't have - camera and artificial star (can be done on a real star but artificial will give better results I think). One needs just to create bunch of aperture masks out of cardboard in 1mm steps and shoot single constant source of light and measure how much light was collected. At some point, there will be change in intensity between different aperture masks and that will tell us how much primary is stopped down by secondary.