catburglar

It depends on your aspirations…I’d agree with @Elp- the pixels are a bit small unless you want to try lucky DSO imaging with exposures <1 second- at F6.3 you’re sampling at about 0.5” per pixel…if lucky imaging is not what you’re after then I think you’d be best to bin x2. But since the chip is a fair bit smaller than APS-C you may be able to increase the spacing between the reducer and the chip to get a bigger reduction factor and still keep good stars in the corners. The ZWO432mm might be a useful alternative- it’s larger pixels give a sampling rate of approx 1.4” per pixel- and the read noise at 140 gain (where HCG kicks in) is approx 4e, similar to the 585 at bin x2…It’s also mono- so more sensitive if smaller galaxies are your target. The 183 or 294 based cameras can also get you in the right ballpark if you choose to bin x4or x3 but you don’t get the zero amp glow technology- this may not be a problem if you’re using the short exposures typical of EEVA.

And I wouldn’t want to talk you out of it…but your initial requirement was for an option of tracking at some point in the future. The EQ5 would probably be a little bulkier than the AZ4 to carry out of the door, but probably still doable in one trip with the OTA mounted…And it could be similarly quick to set up- it only needs to be roughly aligned to North - and the addition of an RA motor gives sidereal rate tracking without any further alignment. The reason I didn’t go down that route was that I always struggled to find stuff with an EQ mount when I first started in astronomy…but it might be something you’d want to consider before you take the plunge…

The high mags I would typically use would be 180x with a 10mm 60 deg AFoV EP or occasionally 257x with a 7mm 82deg AFoV EP- so in both cases I got around 1/3rd of a degree FoV and the object would typically track across the field in 60-80 seconds… So I would just get into the habit of positioning the object at one side of the field observe whilst it tracked across and then reposition…I found it much easier than trying to track in real time…and it soon became second nature. It becomes a bit trickier when the objects are close to the zenith, but I’d just work around that and observe objects whilst they were up to 70-80 degrees altitude. Obviously- that’s not a problem for planets from UK locations😆 I still do the same now with a small mak at circa 180x with a 45 deg AFoV ortho and it’s a pretty relaxing- low tech way to do observe. For what it’s worth, I did also use the 150 on a nexstar 8SE mount and that worked well, but the time it took to align and the absence of manual movement meant that I’d often prefer to use the AZ4 because of it’s simplicity…

I used to own the SW Mak150 and AZ4 on stainless steel tripod- and it was a great combination…but if you want tracking potential in the future an EQ5 class mount is the simplest path. To my knowledge there’s no similarly priced AltAz mount that has a manufacturer upgrade to tracking, but if you’re technically minded you could build something around OnStep that would work and give both goto and tracking… You could go down the manual route now and keep your eyes peeled for a used Nexstar 8SE or Nexstar evolution or iOptron AZ pro, but you’re not going to get one in your budget- but you could recoup a bit by selling the manual mount when the time comes.

For me, the only significant limitation of alt-az mount for EAA is not field rotation per sub because as Mike said each sub is typically pretty short, but field rotation over the duration of the stack. The 585 sensor has the same 1:1.8 aspect ratio as my ASI290, and I think this format exacerbates the effect so that you lose more and more ‘stackable’ FoV as your stack length increases. Obviously the impact varies depending on where in the sky you’re pointing and how big your FoV is to start … but I think with a 4:3 or 1:1 sensor I’d be happy to recommend alt-az, but with your sensor I think some sort of EQ will be preferred. The dob + EQ platform is probably the best of both, if you can live without goto…

I suspect it’s because the orientation of the view is flipped - so you’d need to change that in the view settings…but not sure if that just affects the new images or the entire stack-in which case you’ll still be snookered I suspect…

Another vote for TG365 cover… My SCT has lived outside for 2year+ with no ill effects. I wipe the OTA down at the end of a session if it’s dew covered and give it an occasional airing on bright winter days and a squirt of WD40 on the connectors a couple of times per year… The only bit that comes inside is the Autostar hand controller- that doesn’t seem to like starting up if it’s suffered days of cold…so I always keep it in the house so it starts up warm.

If you want to dabble with planetary imaging a little more (which is how I read your question) then I think I’d take @sorrimen’s advice and try the dob OTA on the EQ5- for the price of some tube rings and a dovetail- what could go wrong… Or a more extravagant option may be to try the dob on a equatorial platform… Both solutions would likely give better quality images for planetary targets than the mak 127 on an EQ5… Although, I’d also agree with the other comments here that a 5 inch mak is a nice scope to have, but I just don’t think it’s the best option available to you for planetary imaging…

If it were me, I think I’d take @ollypenrice’s approach. I suspect bending sheets of ply into a circle wouldn’t give perfection, so you might have to undersize it a bit or take a cutter to it when fitting the obsy. Why choose profile D when profile B has the same protection against water ingress? How high do you want the rebate? As I see it, if you want a perfect circle you’d have to cut circles out of 18mm or 1 inch ply sheet and stack them to the desired height-effectively lose the orange bit in the diagram from @Synchronicity and increase the thickness of the blue bit… You’d have a load of wood wasted, but at least you could make a bench seat and or worktop/shelf unit for inside the obsy with it😜

Yep- that’s one that’s listed in the material on the site too, but I figured it’s such a small chip that you’d struggle to get suitable comp and check stars in the same FoV as the target…on the plus side you probably wouldn’t have to worry about variations in atmospheric absorption because target and comp are at different altitudes. I guess they wouldn’t have built it if there wasn’t a market for it…

I was planning on getting two for my dual rig 😂...as soon as I know what I'd use them for...

+1 for this..I think that's what I was trying to say. Personally I chose the compute stick because of the form factor- I use if for EEVA and it's fine because I only need 2 connections. But in hindsight I should have gone for the more flexible option because now the planets are at a better altitude I'm thinking of giving planetary a go and limited by the eMMC write speed.

Just seen the ASI990MM-PRO listed on FLO (https://www.firstlightoptics.com/zwo-cameras/zwo-asi990mm-pro-swir-short-wave-infrared-dso-cooled-camera.html) Interested to know if anybody can describe the astronomical use case. It's a small chip, big pixel, high read noise camera with extended IR sensitivity but little in the visual range. Puzzled.

I use the Intel Compute Stick version of the Mele 2 for scope control . I think it's the same spec- Intel J4125 CPU, 8GB RAM & 128GB ROM, but limited to only 2 USB ports. I've never used it in anger for planetary imaging but I've just done a test with my ZWO290 mono camera. Running 1920x180 resolution I got about 8-9 fps, at 640x480 RoI I could consistently get 55 fps and with a 320x240 RoI that went up to around 140 fps. So for planetary you'll get reasonable frame rates if you use the RoI feature, but if you wanted to use the full resolution for lunar/solar then you might be limited because of teh relatively low framerate that you may get. That might be improved if you put a M2 disk drive in it and save teh video files to it becuase I expect it could be the write performance of the ROM that's the limiting factor. Edit: I should add my camera is the 290mm mini- which is USB2 speed, but the frame rates I got were significantly lower than the specs suggest, hence I'm guessing that it's something in the PC rather than the USB bus that's limiting the framerate.

My point was that you could have the same RoI size (320x240 pixels say) in both configurations, and if the image scale is the same, then the FoV is the same also and hence - finding and tracking the planet will be just as easy/hard in both configurations… But- I have never tried it and you have, so I’ll pipe down now and leave it to those with some practical experience… Oops- this didn’t come through last night…andI can see you’ve moved past and it’s now irrelevant… just ignore me….walk on by…nothing to see here…

Don’t worry- they’ll cover those topics in their upcoming episode titled: “Visual astronomy before the telescope”…They’re also including archive footage of interviews with Clyde Tombaugh on the discovery of Pluto and David Malin on the application of tricolour photography techniques in astronomy…so it’ll slot in nicely

Just looking back at a few posts from this thread before the show aired- @Jiggy 67was hoping for tips about the entry into astrophotography with a DSLR and @JeremyS was pleased to see any topic about amateur astronomy on the programme… Even if I enjoyed the programme, if I was either of them I’d feel the programme didn’t live up to my expectations based on the title…(although we should also note the title didn’t say amateur astrophotography- it looks like many of us made that connection because of Pete L) Whilst forum members may not be the entirety of the target audience- I’d expect the programmers to offer something to those who are engaged in the hobby… But as has been noted many times, astronomy and this forum are both ‘broad churches’ so there’s never likely to be a one size fits all approach.

@saac I too was informed by the piece on MOONS…but I think it is a stretch too far to think of it as photography…In much the same way that a sketch I make at the eyepiece of my telescope is not astrophotography- yet in both cases we’ve used a device to capture photons from a distant object, processed them in some way and made some sort of pictorial representation of them on some medium that can be viewed by others and interpreted from either (or both) a scientific and aesthetic perspective.

Pete L had a large SCT and Tak Epsilon on show in his garden, both on equatorial mounts- a low cost entry into astrophotography? The smartphone was a good start…but he had a telescope to take the picture of M42…we’ve got no idea what sort of scope it was, could’ve been a cheap’n’cheerful, could’ve been a questar… The issue with this programme was not about affordability it was about useful information- and in this case there was almost nothing useful. I suspect most people actively engaged in astronomy learned nothing about astrophotography and most people who knew little to nothing about astronomy or astrophotography learned almost nothing about that would get them started…apart from the fact that they may be able to do it with a smartphone.

True- there’s lots of content available online, so why do we have any TV programming at all? Surely part of the goal of programmes like Sky at Night is to inform, educate & inspire? Irrespective of what the content could have been, most of the broadcast material was barely relevant to the purported subject of the show. Showing a photo of M31 which led to the discovery of cepheid stars which led to an appreciation of the true scale of the universe says more about astrophysics and cosmology than astrophotography. The MOONS device is actually a tool for spectroscopy not astrophotography. Twilight photos of a crescent moon are barely astrophotography (in much the same way that a daytime photo which includes the sun in the frame is not really astrophotography) Clips of star parties at Sir Patrick’s house have nothing to do with astrophotography….oh no, wait a minute, somebody was taking a photograph so we can include it in the show… Generally, I like the show and am pleased that there’s something astro related still being broadcast…but in this case I was disappointed because it wasn’t what I’d expected to see… Sometimes it’s good to get something unexpected, but not (for me at least) in this case.

I think the focal length/f-ratio (hence which barlow) to use is related to the pixel size and desirable RoI… So a camera with 2 micron pixels at F10 with a 2x barlow will be just as easy (or more likely just as hard) as a camera with 4micron pixels at F/20 with a 4x barlow… There are a few things that could make it planetary imaging easier: 1. Simple Tracking…you may not need or want GoTo, but could you get an equatorial platform for your dob? 2. A bigger RoI…easier to keep the planet in the RoI but this is going to limit frame rate and gobble up your HDD. 3. Capture at ‘sub optimal’ image scale…You may find a camera with 2micron pixels at F5 gives a reasonable image ….but you should know that you’ll not be capturing all that your optics could show you…but if imaging is only an aside, it could be all that you need…

That’s not a bad suggestion…. Clearly some on this forum thought they pitched it about right and others felt it was a missed opportunity…so we should take the opportunity to give some constructive feedback… They’ll never be able to cover all of the details, but something that’s enough to draw new people in would be a good start and like @DaveS I think a bit more explanation of what you need to do to get the image would give people somewhere useful to start from. I think a star trails photo is more impressive than the planetary conjunction shots of Pete’s that they showed...and it’s not rocket science to produce one, then move on to star tracker+DSLR or alt-az scope+webcam- doesn’t need to be super detailed- just the kit that you need, how to focus and do the capture plus some pointers on how to align and stack etc… The minute anyone starts to describe their workflow in PixInsight I’ll be a gonner too, so I’d hope they wouldn’t go that far! PS: I don’t normally knock the show- generally I quite enjoy it, but this seemed like such a missed opportunity I couldn’t help myself but chime in here. I’ll get off my soap box now…

I too was disappointed…I think there was no value in the bits about professional astrophotography- they cover that sort of stuff in almost every other episode and similarly reviewing old clips of Pete Lawrence was a wasted opportunity. It’s impossible to include everything in a single 30mins show, but I think they would have been better to cover two complementary or contrasting aspects in more depth. I think it’s right to cover smartphone and afocal photography- that’s perhaps how many people start. But they didn’t really give anybody a clue as to how they’d go about it other than ‘hold your phone to the eyepiece’. I think they could also have covered one of the following: something about star trackers or lightweight driven mounts as the next step into more complex imaging setups something about planetary imaging- it’s perhaps a bit easier to get started in this sort of imaging compared to deep sky setups. They showed some great pictures of Jupiter and again didn’t give any clues about how to get them something about long exposure imaging with dedicated cmos/ccd cameras to show the sort of setup that’s needed to get the sort of pictures that everybody has seen all over the internet. Whilst they couldn’t go into full detail, these last two aspects get a bit ‘geeky’ quite quickly and if they’d spoken about some of that there’s a chance they’d ignite a spark in someone who is already interested in tech/space/science or just a ‘tinkerer who wants to make stuff work’ to take their first and second steps…

I had one of those a while back and found it needed much less than 50mm to get close to the stated reduction factor- something nearer 35mm if my memory is correct. I think the spacing should be about half the focal length of the reducer- if you project the image of a distant scene onto a wall or card you should be able to get a reasonable idea of the FL and hence the required spacing. I used a couple of screw in eyepiece filters (with the filters removed) screwed in to the end of the camera nosepiece.

Assuming you’re using the lens aperture reasonably wide - I’d be tempted to try 30-60 second lights to minimise any trailing issues… run a couple of test sequences 10x30s, 10x45s etc to see how many keepers you get. Check the histogram from the test shots too, and as long as it’s clear from the y axis you’ll probably be OK.