Penguin

I've taken a library of darks and bias at -10deg and now my subs are stacking ok. Next issue is star trailing even though my PA is good according to SharpCap so I need to get into guiding. Another big subject!

Thanks for your advice guys.

On 28/05/2024 at 16:37, ONIKKINEN said:

To rule out possible calibration issues try with just the lights first. If there is an offset problem between the lights and darks its possible that data is clipped and DSS doesnt know what to do with the data.

But if you want to, do try Siril as it is excellent. Its not nearly as easy to use but it will serve you well when you get the gears rolling with it.

Ah, it was the darks! Took those out and it stacked fine.

Too be honest they looked odd when I was taking them so I should have suspected them from the start. They looked more like light frames even though I took them with the same settings as the lights (180s at 200gain and -10deg) with the scope covered. Maybe the scope cover is not very good and it's letting some light in? Maybe I should take a library of darks with the camera off the scope and capped.

Question: Can I avoid bothering with darks by dithering (is that the term?) the scope between each sub? Maybe I should search the forums or ask a separate question for that.

10 hours ago, ONIKKINEN said:

Drop the star detection threshold all the way to the minimum and see if it finds any stars then, if you haven't tried that already. I found even the minimum threshold a bit too restrictive when i first switched from DSLR to an astro camera, and ultimately switched to Siril which finds hundreds of stars in images where DSS found a handful.

Yep, tried that. The minimum is 2% and it made no difference: still zero stars found. I've never heard of Siril but after a quick Google it looks interesting. I'll try it out when I get a chance.

10 hours ago, Elp said:

Are the stars round?

They're a lot rounder than they have been in the past when my PA was much worse and DSS has never had an issue finding them before. They are at least as round as those in my subs of T Coronae Borealis from the same night. So I don't think that's the issue, but thanks for the suggestion.

Seeing some odd behaviour here. I took 39 90s subs of M81 with my QHY153C through my SW 150P at a gain of 200 (I'm new to a CCD so I don't know the correct settings!)

The subs look ok to me, I can see plenty of stars, but when I register them in DSS, it can't find any and refuses to stack! I've tried changing the star detection threshold from the default as it suggests but that makes no difference. I'm using the same DSS settings I used on T Coronae Borealis (basically, just the recommended settings) and that one registered and stacked absolutely fine.

So what's going on, any ideas?

I've recently acquired a used QHY163C camera to replace my 450D and I'm wondering how that should change the way I do things. Particularly, how do I choose the gain and exposure settings? It's looking through a Skywatcher Explorer 200P with a coma corrector and is on an unguided EQ6-Pro if that makes any difference. Can anyone give examples of suitable starting points? With the 450D I set the ISO to 800 and tended to do 1 minute exposures. I think I now have the alignment sorted so could probably go to 2-minutes and I intend to get into guiding hopefully during this winter.

Thanks for all those hints. I redownloaded and installed the missing solvers and plate solving seems to be working fine again now. Currently imaging the Pacman nebula (I hope, can't see anything looking like a nebula in the raw images at the moment!)

I've downloaded PS3 and ASTAP (there was already an installer for ASTAP in my downloads folder so I think it is what I previously used but it just seemed to have disappeared).

I've also updated APT (from 4.2) to the latest version (4.3) while the laptop was online.

I'll give it another go the next time the sky clears enough so I can see some stars. So that'll probably be in a few months time . 

On 07/10/2023 at 21:55, knobby said:

What solver are you using, I prefer astap, might be worth trying it, also try different exposure times maybe.

Ah, now that I look, I see it doesn't have a 'Near' solver set. That's weird! It definitely used to have one. I set it to PS2 and it started working again, though slower than it used to. That worked for an hour or so and then started timing out on every attempt.

So I've given up on that session (what a frustrating pastime this is!) and come inside to download a few more plate-solving options.

Hi All,

PointCraft in APT has generally been fab with my 450D and SW-250P on EQ6. A few months ago I acquired a 2nd hand QHY163C and this is the first night I've been able to use it. I entered all the configuration for the new camera into APT but after PointCraft has slewed to the target and taken it's first image, I get the error "PointCraft Error: Can't start solving".

The only thing I'm thinking is maybe I need to download some different star charts for the different FOV etc?  Or is there anything else I need to check? 

Now I've been offered a QHY163C for £300. I am very tempted by this, to my limited knowledge it seems like a bargain. Any thoughts?

On 30/05/2023 at 19:31, ollypenrice said:

There may be no point in going for barlows. When it comes to 'getting up close' to a target the significant number is 'arcseconds per pixel.'  This is, even for millionaires, limited by the seeing. Living in SW England you are very unlikely to beat about 1.5 arcsecs per pixel whatever setup you use. Exceptionally, you might but even a sensible optimist will go no better than 1.2 or so.  You can go below that, sure, and get a bigger image of your target but it will contain no more detail than a smaller image. You could get the same result by resampling your smaller image upwards.  The term 'empty resolution' defines larger images containing no new information.

Olly

Yes, I take your point there. All I'm finding in my price range of up to £300 second-hand is planetary cameras, with a very small field of view. I'm not having much luck here! I may have to phone a retailer for suggestions, which I don't want to do since I'm after second hand.

20 hours ago, Budgie1 said:

What do you want it image with the new camera?

The ASI178MC & ASI385MC have very small sensors when compared to your Canon EOS 450D and attached to the Explorer 150P. This is fine if you only want to do planetary or Moon imaging, but makes it tricky for deep sky objects.

There's a Field of View (FOV) calculator as part of Astronomy Tools which will let you play around with different camera/scope combinations to give you an idea of what you'll see. Here's one of M31 with the three cameras you've listed above, plus your Canon. The Altair 183C wasn't in the list so I used the ZWO version with the same sensor.

This is brilliant, thank you so much. I knew there were tools for this sort of thing but hadn't got to grips with them.

So I think something from ZWO with a similar FOV to my 450D is what I want. I have a couple of barlows for smaller targets (assuming they'll still get focus), and now . I'll keep looking on AstroBuySell etc.

I gather that the ASIair doesn't talk to Altair cameras, and as that's likely to be my next purchace, maybe I should be looking at the ZWO options.

Thanks guys, I've now had another look on AstroBuySell and I see three OSC CCD cameras in my price range:

• ZWO ASI 178MC
• Altair Hypercam 183C Pro
• ZWO ASI385MC

Which of these do you think would be a best match for my Skywatcher Explorer 150P? I'm most tempted by the Hypercam but to be honest I haven't even Googled the others!.

I'm most interested in deep-sky: clusters/nebulae/galaxies though I know that even those three have different characteristics an one camera will probably not be great at everything!

Thanks. I've skimmed a couple of review pages and I saw mention that the 183c is designed for refractors.

Quote

With a pixel size of 2.4um, and a sensor size of 16.5 x 12.61mm, this camera will perform best on F/7 refractors or faster.

 I have a Skywatcher Explorer 150P, which I believe is F5, so is the 183c suitable? 

My unmodified 450D has recently died (camera is fine but the USB socket seems dead as the laptop can't see it. checked with multiple laptops and cables so its the port on the camera that's at fault).

So I am looking for a new camera with a stingy budget of below £400. Fortunately, I'm quite happy with 2nd hand! I'm not sure if I should go for a dedicated Astro or another DSLR.

I have no filter wheels so would prefer one-shot colour. I tend to image deep-sky, though I'm not very good at it and don't really want to specialise, which probably makes decisions harder!

I have seen a used Altair 183c for £300 and a Canon 2000D also for £300.

What would you knowledgeable people recommend? Is there such a thing as a reasonable jack-of-all-trades device in that price range?

Thanks, doing a bit of Googling, which I should have done before bothering you guys, all the sites point out the longer focal length and smaller field of view and some say this rules them out for deep sky but other say they are quite versatile (possibly with a focal reducer).

I currently have one of the small guide scope/guide camera kits from FLO so that would be going on it, so not an OAG. What is Differential Flexure? what is it that is flexing in this scenario. Likewise mirror shift, is this just the need to regularly collimate? I'm happy doing that with my 150P, is the process much different with a catadioptric?

My imaging camera is an unmodified Canon 450D so pretty basic. I might go to an ASI colour CCD at some point.

Sounds like they could be a good choice, I'd like to be able get in a little closer to the Crab and Ring nebulae for example, and the planets. But I'm not intending to rush into things!

Hi guys, I'm after a little advice on what sort of OTA I should go for.

TL,DR: Advice wanted on the best type of used OTA at around £500 to go an EQ6-Pro for mainly deep sky photography.

I have recently bought a second-hand EQ6-Pro and am currently trying to sell my HEQ5-Pro + Explorer 150p to recoup some of the EQ6 cost / fund a bigger OTA. I fancy an 8" Schmitt or Maksutov but not for any good reason other than that they look cool! What are they each good for and what are the downsides of them? I don't think I should go for a refractor as they would be too long for the proportions of my observatory. I'd expect to have around £500 to spend and I am very much thinking of used rather than new. Should I stick with a Newtonian? I mainly do mediocre photography of galaxies, clusters and nebulae. but would also be interested in Jupiter, Saturn and Mars.

18 hours ago, david_taurus83 said:

What measurement was the Dec axis?

I didn't measure the Dec axis at the time but I'm pretty sure it had a thin part at the top that the gear was on, then a shoulder and then a thick part, so the thick part was probably 4.9. I'm thinking that mine may have been the one where SkyWatcher ran out of the old stock of motors and moved to the new ones, hence why mine has one of each.

I've sent the motor back to Rother Valley and they will pass it on to Rowan who say they will machine up a part to make it all fit, FOC. So top marks to both companies for customer support.

Oh poop. Thanks, I'll see what Rowan Engineering can do for me.

I have a possible issue when fitting the Rowan Belt mod to my early HEQ-5 Pro and I wonder if anyone can advise:

It's an early mount, as evidenced by the silver setting circles and the fact that the motor fixing plate only has one grub screw for the middle cog.

The issue is that the RA axis motor spindle is significantly narrower than the hole in the sprocket. There is nearly a millimetre of play there (see the attached video clip). The Dec one was nice and snug so I assume it is not supposed to be like this.

Should I crack on regardless? I can tighten it up with the grub-screws obviously be then it will be off centre and that can't be right! The spindle is 4mm diameter and the hole in the sprocket is 4.9mm (see the attached photos) and I don't know which is at fault. I have emailed Rother Valley Optics who supplied the kit in the hopes that the sprocket is faulty and they can just post out a new one.

Hmm, On the Dec axis, I drilled out the plate and the shaft was so snug I had to ease it in with a vice, so I've not bothered with any epoxy. We'll see how it goes.

I now have another issue on the RA axis: the sprocket is really loose one the motor shaft, like there is nearly a millimetre of play! I'll start another topic rather than hijacking this one and I've emailed Rother Valley Optics who supplied my the kit in case they can advise.

And it looks like I have the same issue. already had to fashion my own DIY spindle puller as I forgot to order one with the kit, now I have to drill out the plate as well! So glad I got a drill press for Christmas. 

Well, after trying it on a few targets of the last few months, I have come to the conclusion that it's now worse! I'll confess this may have been caused when, one night, I forgot to park before disconnecting the laptop and then also neglected to turn the power off before closing up the observatory and only realised a couple of days later that it had continued tracking, fouled a shelf and been stuck there all that time. Could that have forced things out of alignment or worse?

Both axis are still free moving with the clutches disengaged so I have improved that aspect, but once the clutches are engaged, there is massive backlash in both. There is a few mm free movement of the ends of the scope in Dec and a similar amount at the end of the counterweight bar in RA. It's obvious to the eye, even from a distance. The slightest further tightening up via the grub screws results in binding.

I have not done guiding before and had bought a guidescope and camera to try it out but PHD2 fails to even calibrate and I am suspecting the backlash is the cause of that. Trying to image targets unguided now leads to me having to throw away around 75% of my subs. Looking back at the history of this thread, you guys have said not to obsess about backlash so maybe it's something else that is wrong and I am barking up the wrong tree.

I'm not sure what to do now. I could look for another 2nd-hand HEQ5-Pro or even an EQ6 but wasn't really expecting to be spending close to 4 figures right now and then what am I going to do with my exiting one? I'd have to inform any potential buyer of my troubles with it. I'm tempted again to send it to DarkFrame for a hypertune. I know people have concerns about their service but I'm hoping that was a temporary blip that they have since sorted.