vlaiv

https://www.teleskop-express.de/shop/product_info.php/info/p339_Astronomik-ASGruen1---Green-Interference-Filter--1-25-inch-filter-thread.html Not quite steep cut off - but it does cover the range you mentioned.

I don't think anyone's is to be fair. Neither cones: nor rods: are sensitive to anything above 700nm

Well if you don't guide - you get "natural dithering" due to mount PE and PA error, so no bonus there really

These days autoguiding is really a norm - everyone who is serious about AP is doing it. Mount can track the sky - but mounts are not perfect. Even very expensive mounts have imperfections in mechanical parts - parts that need to be round are not really round - they end up being "egg shaped". This can't be seen by naked eye or felt - but it shows up as periodic error in tracking. Mount can't hold star steady - in single place for a long period of time. Look at this recording of my HEQ5 over an hour without guiding: (it is sped up of course). Up / down motion is due to periodic error in gears that drive the mount. Left to right motion is due to poor polar alignment. Each of these two limit how long you can expose before star trailing becomes an issue. If you want to image without guiding - you can, but you need mount with good absolute encoders, and these cost as much as whole Heq5 to be added to a mount. For example iOptron CEM26 costs about £1000 in basic version: https://www.firstlightoptics.com/ioptron-mounts/ioptron-cem26-center-balanced-equatorial-goto-mount.html but same mount costs £2000 with encoders: https://www.firstlightoptics.com/ioptron-mounts/ioptron-cem26-ec-center-balanced-equatorial-goto-mount-with-encoders.html Auto guiding is much cheaper than that (even if you don't have laptop - you can use raspberry pi to control the mount and guide and control that with your smart phone). Also note that autoguiding is something that you can add later on. You can start by simply doing shorter exposures like 30s to a minute and discarding some of your frames if they show excessive trailing in stars. That will get you going and you'll be able to learn basic steps in imaging and processing and later you can add auto guiding to improve performance. I'm not sure what to say about AVX. Haven't used it, haven't read much about it. If you think it will provide you with better tracking performance without the need for auto guiding - it won't. Very few mounts are capable of tracking without guiding and all are expensive

It is a bit bigger and yes, it catches wind a bit more, but its both issue and not an issue - depending on how you look at it. HEQ5 can mount much bigger scopes: Yep, that is HEQ5 with 1.2 meter 8" newtonian that weighs around 11Kg - by itself with 1Kg guide scope + guider and camera and mount rings - all approaching max capacity of the mount. I needed 15Kg of counter weights to balance it all - and yes, it did manage to produce image: however, above setup is not something I would recommend (to anyone, let alone someone just starting out). By comparison - both 130PDS and 150PDS are small, short scopes. Yes, 150PDS will catch a bit more wind - on a really windy day, but if day is windy - even 130PDS will have some issues. You can overcome that by putting mount / scope somewhere that is shielded from wind - or just avoiding to shoot on nights where wind is 6+ m/s Very few scopes can capture Andromeda in a single go - you need wide field scope to properly frame it. That does not mean that you can't take a photo of it. There is something called mosaic technique. You take two or four images of different parts of target and you put those together to create final image I could not fit whole M31 on my sensor with 380mm FL scope (80mm f/6 reduced to x0.8): but I was able to make wide shot of M42 with very small sensor (guide camera really) - by making 3x3 mosaic (this version clearly shows pattern as I did not take flats and dust shadows show nicely): Btw 150PDS will also beat both 70-80mm APO and 130PDS on visual targets as well.

None what so ever, but difference in declination of the target might have something to do with it. Mount tracks the best near Polaris - where actual movement is close to 0 (mount does move, but frame is pretty much stationary - it only rotates once in 24h). Worst mount performance is at declination 0. That is simply wrong - especially if you happen to use large number of subs. Each time you double number of subs you stack - you add another bit of precision. It takes only 4 subs stacked to get from 14bit precision to 16bit precision. Anything above that is simply subject to rounding errors. 32bit float point precision does not suffer from that. Explanation is rather technical, but I did write about it recently here on SGL as for the rest of it, I gave what I believe is best advice, so won't be repeating myself

This is what I would do: - calibrate each set of lights with their own calibration subs - choose what resolution you'll work with - either 2.88"/px or 2.33"/px and register all subs against sub from respective set. I'd advise you to go with 2.88"/px rather than 2.33"/px as downsampling will have edge in sharpness and definition over up sampling - use smart stacking algorithm that is capable of stacking two sets of subs having very different SNR Problem is of course with point number 3 Most stacking algorithms assign single weight for subs - and that is not good approach because there is no single SNR value in sub. In fact, every pixel will have some signal and some associated noise and ratio of these two quantities will be very different (just think nebulosity and background - one contains signal and other does not, so no way they can have same SNR but they do belong to same sub). Solution to point three is - use algorithm that I developed that is capable of using subs with very different SNRs across the board . Read about it here: If you are interested, I'll share ImageJ plugins needed to do the stacking and explain how to use them.

Yes, it gives time, target coordinates and approximate shooting location With such early target I wondered about astronomical darkness and twilight, but it was still deep darkness. Indeed, there can be quite a bit of variation. There is handy tool called SQC - sky quality camera software - that I can't find anywhere online - except results. You can see those on lightpollutionmap.info when you turn on SQC measurement - it looks like this: With simple guide camera and all sky lens - we could do something similar - create map of LP for our locations (above image is actually fairly close to my current location - about few km away).

Why do you think it should be higher rather than lower? High guide rate works good with mechanically sound / stiff mounts that respond well to sudden changes in speed. Entry level mounts that have backlash, are lighter in comparison to weight they are carrying and are in general wobbly - don't cope well with acceleration and jerk.

I got SQM of 16.97, so quite close to your original estimate of SQM 17.8 As far as I can tell - that is normal, even if your site is not that bright at zenith. Target is at alt 30° as far as I can tell from the data and in direction of major LP source - Helsinki. You are on border of red and white zone at SQM 19.5 judging by lightpollutionmap.info so above SQM17 is to be expected under given circumstances.

Well, if you post single frame and flat, flat dark and dark master - I'd be happy to do it for you and make walk thru for doing it in ImageJ / AstroImageJ

Here is simple guide on how to best to do it: 1. calibrate your sub properly (remove dark current and apply master flat) 2. since it is OSC - do bayer split rather than debayering and take one green sub image to work on (this will reduce your pixel scale by factor of two - but it does not matter if you plate solve) 3. plate solve to get pixel scale 4. convert ADU values to electrons 5. select "empty" part of the image and measure median - convert to electrons per arc second squared with pixel scale (don't divide with exposure - no need) 6. find star of known magnitude that is not clipping and measure its flux 7. find sky brightness in magnitudes by flux ratio between star and background

It should not be hard to distinguish between the two. Atmospheric dispersion is usually linear. One side is bluish while other side is red: CA is the same all around (usually blue). Depending on eyepieces used - you might also get some lateral CA - this happens with wide field eyepieces at the edge of the field and depends on eye placement

FLO has section on returned items - check it here: https://www.firstlightoptics.com/offers.html They usually give 10% for customer returns and refurbished items. Check out your local forums as well. Don't know where are you from - but you might have something on offer there (in my country there is relatively small astro amateur scene so second hand items don't come by often). With second hand items, it is nice that you might be able to try it out and make sure everything is all right (I guess that depends now on active C19 measures). How good are you with DIY? Maybe you could build small dob mount like this one: https://www.astroshop.eu/alt-azimuth-without-goto/omegon-mini-ii-dobsonian-mount/p,53648 (this actual mount is too small to hold the scope like 130PDS - but just to give you idea - all you need is couple of pieces of plywood / MDF cut to shape, bearings, some PTFE pads and one vixen clamp).

Did you image M31 recently? Maybe you captured V1? https://esahubble.org/images/opo1115a/ I actually identified it in amateur M31 images few times. Here it is in my M31 image: Here is guide how to find it:

Don't even think about alt-az or dob mount for AP if you are serious about it. In principle - you can use very short exposures like second or two - to do very basic astrophotography with driven alt-az mount - but that is for very basic images. For anything more serious than that - you want EQ tracking mount. Even simple star tracker will be more rewarding for someone starting into AP than alt-az mount. There actually is, it is very recent addition: https://www.firstlightoptics.com/heritage/sky-watcher-heritage-150p-flextube-virtuoso-gti.html That is 150/750 newtonian with motorized alt/az mount and goto capability. HEQ5 is very nice AP mount and more than capable mount for visual. I have HEQ5 - and almost never use it for visual. For visual I have simpler mounts. I use dob mount for my 8" dobsonian, and Az4 mount for smaller refractors. I much prefer simpler manual mounts for observing then setting up heavy EQ type mount for that. In reality - you can get very capable visual scope for small amount of money and even basic AP setup is going to cost you much more - like x4-5 more than that. Have you considered purchasing second hand items? That way you can save some money?

130PDS offers better view visually - images will be brighter and there will be more details on the planets / moon. Only issue with it is that it is newtonian type telescope and you'll be using it on EQ mount. Not the best combination. As mount tracks across the sky - eyepiece will end up in very strange positions and you'll need to constantly rotate the telescope in tube rings to make eyepiece accessible. Newtonian is much better suited to alt az type mount. What's your budget? How about getting two scopes? I know that this sounds silly - but why not go for 130mm collapsible newtonian on dob mount. This telescope is much more suitable for children to use: https://www.firstlightoptics.com/reflectors/skywatcher-heritage-130p-flextube.html That way you can have good scope for visual and still get APO to do astrophotography with?

Indeed - both images look like they would be otherwise fine - except for the focus issue. That is the first thing to sort out.

They can actually be stars - very hot, very big, young stars. Such stars can have luminosity that is up to 1,000,000 times larger than our Sun. Relative luminosity falls of with square of distance, so this sort of star will have same brightness if it is x1000 further away. Since M33 is 3.2Mly - it is like looking at a G2V star that is 3.2Kly away or 3200Ly away. That is not very far and you can easily image such star. You can take a look at Hubble images of M33 and M31 and see individual large stars being resolved: In fact - you can compare the two: I've marked two yellow stars and in "direction" they are pointing is star forming region.

Your mount simply does not respond to guide pulses under your settings: RA error is much larger than DEC error and you have elongation in RA direction. Set your guide speed at x0.5 sidereal or slower, use default settings ( too low aggressiveness in RA), calibrate near meridian and equator and use at least 2s guide exposures. Make your setup east heavy - to eliminate any excessive backlash in RA

Apart from being seriously out of focus - I see no issue with the data.

Simplest thing you can do to see if it is due to way you integrate - is just use simplest average integration without any normalization / pixel rejections / whatever for everything. Create master calibration frames and integrate image like that - no weights no fancy stuff - just simple average. Sure image might not look the best and there will be hot pixels and all - but at this stage you don't care about it - you just want to see if your calibration works and if using advanced stuff is causing you issues. If you get clean result - then you can start narrowing down for the cause of issue (and be happy as your camera / calibration works as it should).

I have 80mm APO scope for astrophotography, and you can't go wrong with that. It is this one: https://www.teleskop-express.de/shop/product_info.php/info/p3881_TS-Optics-PHOTOLINE-80mm-f-6-FPL53-Triplet-APO---2-5--RAP-Focuser.html One I have is very good scope, and is excellent astrophotography scope - wider field one. However, 130PDS will have significant edge visually - both on DSO and on planets. This is actually very hard to give advice on - should you go for 80mm scope or stick with 130PDS. 130PDS is a bit more "all around" focal length at 650mm. ~80mm APO, paired with field flattener / reducer is more 350-400mm focal length - it is really getting into wide field rather than all around. With refractor - it is all about simplicity - just put camera on and shoot. Newtonians are bigger and more susceptible to wind and there is collimation, and are often mechanically less rigid (focuser can be tilted for example) and so on. But 130PDS is very nice imaging scope - there are a lot of nice images produced with it - there is a whole thread here on SGL dedicated to that scope and images people produce with it. Here is best I can do to help you decide: - 130PDS will have edge on visual and be more general imaging scope while small apo will be good wide field instrument for both observing and imaging - If I was choosing for myself as first scope - I'd go with 130PDS - If I'm advising complete novice - I'd say go with 70-80mm APO (there is a lot to learn and master in imaging and if that is your main goal - and it looks like it is - then go with that scope).

To get the idea of what your "top" working resolution should be - take any of your old subs you shot with TS 130mm and measure star FWHM in arc seconds. You'll get range of values - depending on how good seeing was at particular instance (and your focusing of course - pick subs with good focus) and how your mount performed at the time - divide that with 1.6 and that is pixel scale that is suitable for given image. My guess is - more often than not you'll be above 1.5"/px - approaching 2"/px. Larger aperture will give you slightly smaller FWHM - and hence possibility for higher working resolution - but not by much. Maybe shave off 0.1 to 0.2"/px from your 130mm when using 8" aperture if you leave everything else the same (mount and sky).

At those prices, I'm standing by and waving to the passing bandwagons