pete_81

🤣 Very true!

Interesting thread, thought I'd add my $0.02... Surely the f/# of an optical system is a measure of how many photons are hitting unit area. Bear with me on that - one thing that stands out at photography club is that taking an image with same ISO, shutter speed and f/# has the 'subject' of the image at the same brightness regardless of the focal length. The focal length changes the zoom, but I use zoom loosely here, as it actually changes the "field of view", which also depends on camera sensor size, etc etc. I have cropped sensors and have tried to get away from the 'effective focal ratio' as it's not really true - my cropped sensor has a field of view less than a full frame sensor, more due to the sensor size. Yes, I know it's the "equivalent focal length" but it's a dangerous term in my view. Coming back to the f/# - here's an interesting thing... Hubble is rated at f/24, (D=2.4m, F=57.6m) so I can take HST on with my much faster f/4.9 500mm telescope - I can take an image the same brightness as HST in 4%(ish) of the time (5 stops ish)! What I cannot match is the "zoom" where HST has ~100x more (assuming the same sensor size would remain unchanged), and as for the light pollution and atmospheric disturbances I suffer from, I don't have any real chances of competing with the HST imaging capability! HST can expose for longer without worrying about cooling (outer space is a tad cooler than a ZWO can manage!) and kicks my amateurish field of views out of the game before I even open ClearOutside to see if there is any point in getting my mount out! Making larger aperture scopes allows imaging time to reduce ("faster", as the f/# decreases) or keep f/# same by increasing focal length, increasing "zoom/magnification/FoV" so resolving finer details. Yes, for visual the f/ratio is not seen as being as useful when we use exit pupil, but then again the exit pupil comes from the aperture anyway so a "faster" scope has a larger exit pupil for the same FOV! And we go around in circles! I know the thing that got me was how I see the f/# now - effectively a measure of number of photons hitting sensor per unit area, and changing my camera lens focal length definition from "zoom" to "FoV for given sensor".

Hi Zach, Apologies if I've misunderstood/misled you/anyone (from Ian's comment, it may appear that I've said "NO! You can't do that!"). My message was just hoping to show my experiences and possibly planning a bit longer-term, sorry if misunderstood and there's too much 'my spin' on it. I'm hoping it is taken as advice more than anything else. Yes, budget is the biggest question, especially imaging - it is an endless money pit! Initially, is it fair to say that you're interested in visual to start, hence buying (and cancelling) the dob? If you're interested in starting with visual, here's a really good page about visual expectations: https://stargazerslounge.com/topic/196278-what-can-i-expect-to-see/. Also have a look at "Turn Left At Orion" book. I've been there (and sure most have), looking through scope and (a little) disheartened that the targets didn't look like the photos I'd see in books and publications, then took interest in just getting out and learning my way around the heavens. With that, I must add that there is NEVER an occasion that I have when doing visual that I'm ever not 'wowed' by just 'looking' at the sky, even now (moon, planets, and just random locations in the heavens) by the sheer number of stars just popping out of the blackness! If you're looking to start with visual, any telescope (from decent supplier) should be in the offerings for you, within the understanding that it's still not a one-does-all. HappyKat points out about existing 5D lenses - yep, they'll (be a great) start you on you AP journey, but won't help visual astronomy. Any interest (potential future proofing) for imaging and the mount question becomes 'can you stretch a bit'... The reason for this is whilst the AZ *can* be used for AP, it's not a long-term solution for most - everyone agrees above - no denying it's just not the preferred "way to do it", certainly for longer exposures. To throw another spanner in the works - what about the possibility of a tracking mount that you can use for AP (star-adventurer for example) and a decent set of binoculars? My bug for astro was with a 10x50 which resolved Jupiter & the 4-Galilean moons. Perhaps browse to see what others see with binoculars as they're frequently recommended to travel to dark sites with (quick to set up too!)?

I've just purchased a (second-hand) ST102 and using it to get into AP. The issue I see in your plan is the Alt-AZ mount. Basically, whilst this mount can 'track' the night sky motion from East-West, it doesn't rotate with it on what we call the Equatorial. I have a very large telescope (well, 1.2m length, 250mm diameter) and had the issue with it that I only used it to do 'visual' observing but then wanted to start a little AP so needed a (£1.5k) mount to cope with it. I've still not used this for imaging, but rather used my camera lenses with the very expensive tripod to track the night sky and start into AP. Then got the ST102 to use a 'telescope' and get started into AP with telescope. I'd agree with Clarkey's comment - possibly the tracking mount and use your DSLR gear, then invest in a better mount & scope and build up from there. Lazy Astronomer's comment about the endless rabbit hole though... VERY true! Are you more interested in visual or doing imaging? If only the latter, then that's ok - use a tracking mount with DSLR. If visual (adding eyepieces to camera lenses just isn't done, so) you'll need telescope and use for both. Don't dismiss the ST102 as imaging potential though, it's cheaper and you can upgrade once you've got the bug. But mount is probably the thing to pay attention to. HTH

Thanks very much for that Wim. Yes, using (modded) DSLR as the astro cams really just can't be justified until I get a decent workflow and more likely location. Home is in Bortle 6, so not really the best, but the local bakery has floodlights on all night which do tend to light the garden a bit. Did start a thread about exposures to use as a starting point, along with ISO setting which sparked the usual comments - use the native ISO of camera for max DR (hence my using ISO200 as standard). But in short, my idea of multiple durations isn't ideal as you're recommending more shorter exposures (but ultimately the integration time is there as there, just with more images to process with), whilst ideally avoiding saturated stars. Anyone else wanting to comment on this - "just do more, shorter exposures to avoid saturation"?

Thanks @vlaiv, So quick search for that technique also gave old thread that agreed with what you say above https://stargazerslounge.com/topic/60705-dss-entropy-weighted-average-hdr-stacking/ So shall give it a go and see. Guess the question is to use this method just once with all loaded images, or to do light, dark, flat & Bias stack for each exposure, then do a stack using the result from each. More reading required but certainly looks promising!

Nope, filter clean. Was cleaned with IPA just before going into the filter wheel and all inspected before closing the wheel. It was more the 'jittery' star trail that it has: To me, it looks like the guiding got lost for a bit. I had thought it was clear through the time the images were taken, and to all have the same effect (1hr15m) again doesn't fit this argument, bearing in mind the plate solving didn't need to move when changing to the UV/IR filter and target was bang centre. Wondered if there was a dither setting wrong, but it's only using a couple of pixels every 3rd frame. Best I can assume is the wind but seems odd that the shorter exposures (similar breezes) don't show (I didn't look at the guiding graph so it's more a lesson to watch and take diagnostics for everything if possible, hence doing the PA screenshot!). Hmmm... I'll do again at some point and watch guiding and so on I guess.

Still getting ideas together So when imaging, DSOs need minutes to get enough light into the sensor but the dynamic range of cameras just isn't sufficient (stars very blown-out and stretching leading to noisy DSOs) - what's the solution? Do short exposures to get stars good (and you obviously don't need too many of these) and (more) longer exposures to bring out DSOs (and then even longer exposures for the dimmer regions, accompanied by complex masking and stacking)? And obviously darks associated with each of the exposures? Then flats & bias images for the session too? Then stack darks & lights of each exposure (with master flats & bias) and blend each exposure together bringing out the 'HDR' image, or can DSS (for example) handle the saturated areas of an image and use the shorter exposures for these regions automatically? I doubt the latter but would be nice, wouldn't it?!

Went for North America Nebula the other night, and having already done some shots with astro-modded DSLR, thought to try Ha which would allow experimenting with the 7nm Baader, option for luminance layers (APP layering) and longer exposure experimentation. Polar alignment was good enough for the evening (16" out) and plate solving successully pinned down the nebula. Guiding also running with dithering etc. But when the first of the (5min) Ha images popped up, I noted the bright stars were streaking with ISO 200 so thought I'd up ISO to see if it was just a display artefact and same thing. ISO 200 ISO 1600 Guiding looked OK with settings as used before, but obviously not sure what was going on. All 15 images were the same with streaky stars. So reduced exposure to 2min and went for the visible (UV/IR filter) and those worked fine, so built up more images to stack with 2 & 3 min shots. No streaking on any of these. Final stack from this session: Any ideas what the trails are caused by? It was quite breezy, but assumed the 3min exposures would have had similar artefacts if it was the wind catching the scope.

Nice job Alex!

For further progress on this project, I have purchased all the bits to make a battery box containing all I need at this stage. I have no cooling (DSLR) and no electronic focuser or electric filter wheel (manual wheel just acquired), so think that is my go-to setup. The following kit needs power: AZEQ6 mount, 12V, 4A (slewing power requirement, not tracking/guiding) DSLR (Canon 550D), 8V, 2A RPi (pi4, 4GB), 5V, 3A Dew Heaters (USB), 5V, 2A, x2 So following Paul's @wookie1965 plan above, got a master switch, in-line fuse and blade-fuse box (included -ve busbar) to supply the following connections: The 5-switches on the 12V panel will control (individually): Cigarette Socket (for AZEQ6 connection using existing power cable) Voltage Supply Reading (for temporary viewing of battery supply) USB ports (double 2.1A) to supply dew heaters when used (one for main scope, 1 for guide scope) Banana plug socket, for feeding power to Buck Converter DC Connector (2.1/5.5) for powering step-down converter Also adding the Battery Studs for easier charging of the battery. Total cost for the above: just over £35. Already used with the Nevada unit, I have the cigarette socket and banana connector similar to above. (I've also made a male-banana to female-banana/DC connector, so this splitter is identical to the 2 single components above, so connections are transferrable). I've not used the heaters yet, but at home can use power bank battery to feed them, but would like to do all (or at least be able to do all) from one supply, hence the panel purchase. So I have already got some of the above implemented with my setup as below: For the female banana plug socket, I have male plugs attached to a 12V-5V buck converter, and this then powers the RPi via a USB_A to USB_C cable. The DC socket connector feeds into a 12V-8V Step Down Battery for the DSLR. That's it, all connections and cables obtained and ready. So successfully used this setup at home, hence trying to resemble the same for in the field - the connectors at the top would be connected to the 'dark-site kit' that I'm hoping to utilise in the colder, darker evenings - how many dark sites have power to them is the main reason for all this I guess! Still have to decide on what battery to get, but for the specs above, I estimate the following power required: Mount: 12V x 4A = 48W (overkill, but work with maximum requirement) Camera: 8V x 2A = 16W RPi: 5V x 3A = 15W Heaters: 5V x 4A = 20W ===== 100W (rounded up and assuming all converters are efficient) So at 12V, realistically no less than (100W ÷ 12V) 8A required, and during winter, hours of darkness are pretty decent - I'd guess one could easily look at >6hrs imaging a night at dark site with no other sources of power, so 54Ah - I reckon I'm going to be looking at no less than a 110Ah leisure battery?! (to ensure not running it to 50% capacity which is what I think I've seen around)! What are others using and recommendations based on the above?

As a glasses wearer, I'm always amazed how dusty and greasy my spectacles are and how much I can see through them when in that state! Same issue for reflector telescopes - the general advice is don't clean unless you *really* have to. My advice would be similar to above (Pete Presland) - use the blower to remove coarse dirt/dust of EPs (and front elements/primary of telescopes occasionally) and then leave alone until they get so dire that you have to clean them (similar to specs!)

Further reading and emailing FLO, I'll post quickly my findings. I found the post How Parfocal Are Filters and FLO response suggest that yes, reasonable focus should be achievable with the UV/IR, but although claiming parfocal, minor optimisation is required for each filter. Can anyone help with the threads question - what is the difference between M42, M48 and T-Mount (I suspect T and M42 are identical threads, and M48 is then just larger, but can someone confirm/correct this!)

Seeing that you've just done, missed the chance to suggest going down the route of the mini-PC (raspberry pi) for £100 with case, power, etc. Only need monitor to run it (or connect via vnc), just thought that looks like Amazon listing so you could think about this as a much cheaper option but commonly used on setups (not that I'm biased!). I didn't know they existed or were as good (sole purpose of mine and many on here is for astro)

As a daytime photographer, the monitor is unfortunately the most important piece of kit - you'll want to get something that has a large "gamut" - the internet and phones generally use the sRGB colour standard, and most modest monitors should cover the vast majority of this 'colour space'. https://www.trustedreviews.com/news/monitor-colour-spaces-adobergb-srgb-2949078 All it really means is that the colours your image has will appear 'true' on the monitor (blacks appearing as deep black, whites as bright clean whites, and this follows for the RGB channels). What I'd possibly suggest spend a reasonable amount on a monitor, then use a colorimeter on your new monitor - this sets up the colours correctly so the image you're processing will look the same on other screens - this is then the other debate on how good the 'viewers screens' are! Google about it, and here's a great post https://arstechnica.com/civis/viewtopic.php?f=6&t=1430001 I've a Macbook Pro and I think on my last calibration I read that I am using 99% of the sRGB spectrum. Don't go down the money hole of a full Adobe RGB spectrum monitor (the Adobe spectrum is MUCH larger than the sRGB), unless you're gaming/photographing for profit. Only my $0.02, but you'll not benefit from it, nor will your pocket! Spend on the colorimeter first, you may even find your old laptop monitor improves with a colour calibration. The big names in this are 'SPYDER' (I have the Spyder 5 Express) and 'ColorMunki'. The higher end can also calibrate the colours of your printer, ink and paper, but again that's another topic! HTH

So using a filter wheel, I can have several filters quickly available and easy to use. We all know this We also know that adding a filter changes the position of the final image, slightly, so refocus is required if a filter is added. To achieve focus, on a DSLR, generally view live-mode and use a Bahtinov mask. Everyone still following, good When using narrowband filters, this is made a bit more tricky, as there just isn't the same light coming through. 2 possible solutions... Use either take long exposures (several seconds) to do focus, or some may know that Baader do a nice 'Clear' filter that has the same optical path length as their filters - so focus with the clear filter and then change the filter wheel to the narrowband and although the image may not be visible, one can be happy that things are in focus. So my question in short is can I use my Baader UV/IR cut filter instead of requiring another purchase(🤣!) of the clear glass filter, or just accept the 'no takeout tonight family!' Also, quick question about connections - M42, M48 and T-mount - from what I've seen, the T-mount is equivalent threading to the M42, just that it's specific to a camera flange (eg Canon-Tmount has a Canon bayonet and M42 (.75 pitch) thread on each side of the adapter?

Thanks @happy-kat! It's more the 102 isn't going to match to a Zenithstar, but still give some decent images. I've followed horfield-astro and seen his images initially done with the ST102 so know it's not going to give HST competition, but still very nice images Yep, 3D printer just about to go to work on cable holder for the dovetail, doing some measurements for the mask later this evening, as surprise surprise, clouds forecast!

Thanks again @alacant for the advice you suggest. So, asking the dumb questions on each... Why lose the darks? Flats are obviously sensible to avoid/compensate for vignettes and dust spots Dithering, check, was using in the guiding. Think I had it set to 3/4 pixels. Would anyone recommend different settings with focal length of guide scope at half that of the imaging (pixel sizes similar)? Cleaning sensor, on the list to do at some point, but wanting to do more with setup and post than worry about this just atm. Covering VF, check I used DSS via OS-X and Parallels to run Windows. Repeated using the clipping "intersection" mode. Just browsing Siril atm as this works natively on OS-X so might be attractive alternative to DSS. Anyone any opinions on either or? I've assumed DSS had got the bayer mask correct, and reading around, it looks like the regular RGGB is correct - any reason you say this? Just sanity check? @happy-kat, thanks for your posts on the image processing. Scope is the StarTravel102 (purchased off SGL and this is the first imaging session it's had with me). I honestly was expecting CA as it's very much a starting telescope, but beats the Tamron500 f/8 mirror lens I'd previously been using and lets me get into imaging with a telescope (so it looks better on the AZEQ6 too!). I'll do more images but good to know there is some data there. No surprises, I looked in the red channel and much more structure there, so will also have a try with the Ha and see if I can get more detail out of that. Does plate solving still do OK with such a filter in place or am I about to need a filter wheel to eliminate the requirement of camera on and off to add filters?!

Thanks Tony, Yep, flats were next on job. If I'm right in thinking this, I can do several flat images and they'll then form a master flat for the DSLR and telescope combo, isn't that right? If I wanted to build a library, ISO really doesn't matter (unlike darks) so several images should do the job...

Ummm, so that's come back showing that it is indeed NGC7000 Looks pretty central too, so have to assume the alignment, guiding etc has been pretty decent. Anyone care to comment on this assumption as it's my first attempt at this?!

OK, so to plate-solve the image, I've uploaded a temporary png to Astrometry.net Assuming this is right. Just waiting for results...

@happy-kat, nope in short! Thought plate solving was about telescope alignment (polar alignment routine in KStars, and then done again after 'going to' target to make sure image is seeing the right thing. This imaging set is the first time I used plate solving ever - heard good things about it, but was a little nervous about it being an advanced and therefore complicated process... Wow, at least for what I think I've done with it, it is VERY simple and such a good idea! So, the session consisted of: setup scope, camera, etc, balanced everything then did rough polar alignment via polar scope. This was ROUGH - didn't open the app to see where Polaris should have been, just that it was within the clock on the polarscope - the plan was always to use EKOS to plate-solve the alignment and get polar aligned better this way. So using the polar alignment routine in KStars/EKOS, it reported some 30'. I followed the routine and ended up with both Alt & Az being green (both < 1'). Then 'goto' NGC7000 and plate solved position (synced the mount position into KStars and it was just off slightly, so did another go-to and after the small motion, a final plate solve showed it centred on the nebula. So how to plate-solve the image? Can you help there please! Just redoing the stack now following the guides (haven't ever touched DSS settings, so hoping that outputting to FITS is the only real difference) Anyone had a go at the image?! Tips on imaging, (stars are saturated me thinks!) and processing really appreciated.

So another muppet that hasn't a clue really! Sorry in advance. Not really looking for this to be a thread on how good/bad my images taken are as that's for another forum and how to use the hardware (camera, telescope, polar aligning, guiding, etc), but more how to get an image from DSLR to impressive image. Image was of NorthAmerica Nebula, NGC7000, 120x1min lights, 60x1min darks. ISO200, f/4.9 at 500mm. I've had a go with Startools and followed the suggested workflow on the website and was pleased with the output My workflow obviously needs addressing, but I've used the following edits: Import Tiff, Linear unstretched. AutoDev, selecting ROI less couple of hundred pixels on each edge Bin at 50% Crop edges similar to ROI Wipe (default settings) FilmDev => digital 97%,Gamma0.75, RGB_L 100% each, WB UseStars (dark anomolies didn't appear to change much at this point) Contrast => BASIC preset, Locality 75%, other settings left HDR => Tame preset Other panels not really touched or more that I didn't either know what I was doing or didn't like the result Here's what I came up with and nebulosity is nicely visible but not a very impressive punchy image. Affinity obviously gave something completely different, where I concentrated a little more on the nebula but I'm sure most would agree that I haven't got a clue where to start! I'd love folks to have a go at editing the raw in APP/Photoshop and summarise layer settings used - I've gone mainly with levels, curves, brightness and contrast and used about 15 adjustment layers all in all, which I think is going down the wrong route (especially as they're all the same type of adjustments!) eg my first 5 layers are Brite&Contr, 100/0 100/0 50/0 0/100 0/80, then a contrast curve and astrostretch curve (arcsinh), then more of the same. I'm really keen on getting into the edits, but there are clearly many filter/layer options I am unaware of, and how they work with the images. It might be a bit of a cop-out by asking for how others would edit this specifically, but truthfully any help is appreciated on this! Thanks so much in advance DSS Stack Output.TIF

At last with the clear skies! Can't remember when we last had them! Thought I'd send in my setup which allowed a comfortable 2hrs of lights and 1hr of darks, after learning polar alignment and plate solving with KStars/EKOS, so simple and so glad I've found out how to use it! Rather pleased that I have virtually no excess cables anywhere, all short USBs to the RPi and then power to the RPi, camera and mount are the only cables dangling anywhere. About to also add buck converter for camera too so only one power socket controlling the lot, then this will transfer to dark-site with single battery (or at least that's the plan!) Just to work out the best workflow of image processing! Hoping for more clear skies later this week for us all!

Thanks Paul, This is great and hope it may help others that have the same dilema! Pete