LowGravitas

Okay. So I git the plate-sloving working. However, oddly, the position of the virtual pole, even when apparently perfectly polar aligned, changes drastically when I rotate the mount in RA.

Why might that be?

I'll give reinstallation a try. I am in a Bortle 7 zone, but in the split second moments in which it states plate-solving has succeeded it's detecting around 20-25 stars.

Hi. I just got an iPolar. The issue is that the somehow it works very fast, the text on the upper left corner where it tells you what to do goes so fast that you cannot read it. The circle that is supposed to be moved to the cross keeps jumping around, and I mean by a lot.

Latitude and Longitude is correct. When I take the thing off and look through the optical scope, Polaris is in the fov. I don't know what's wring with the thing.

14 hours ago, Davey-T said:

Looks good, is that the full frame or cropped.

There is a long running thread titled Imaging with the Star Adventurer perhaps you could post it in there as well.

Dave

Oh, I forgot to mention that it has indeed been somewhat cropped.

Some details concerning the image:

-Equipment

Redcat 51 on a Star Adventurer with a modded Canon 600D.

-Acquisition

281 x 30 second lights @ ISO 800, and 50 biases. Taken in a Bortle 7 location.

-Processing

Stacking was performed using the relevant script in Siril. Levels and curves adjustment in Photoshop, as well as saturation and colour balance adjustments. Noise reduction in Camera Raw.

So, you don't think I should be concerned? I can't say I'm knowledgeable about the weight bearing properties of screws haha.

Huh. And I assume you've used it for some time without issue?

Thanks.

e: I also wonder what causes it

The screw that fastens my Star Adventurer to the proprietary equatorial wedge appears to have been damaged, somehow (see picture). The metal at its base seems to have fractured in multiple places.

In this state, I don't know if I trust it to support the weight of over £1000 worth of equipment.

Does anyone know where to get a replacement? I don't know if it's a generic design, or something specifically made for the task by Sky-Watcher. In any case, any help would be appreciated!

Does anyone know the weight capacity of this tripod?:

https://www.firstlightoptics.com/tripods/horizon-8115-2-way-heavy-duty-tripod.html

I cannot seem to find it anywhere. I was planning on using it (with the head removed) with a Star Adventurer Pro, Redcat 51, and Canon 600D/T3i.

9 minutes ago, Knight of Clear Skies said:

Decent enough image but it's not focused on infinity, so doesn't help with the diagnostics I'm afraid. A quick snap of the Moon might be easiest way to test it.

Yeah. Will do so when the clouds next clear.

3 hours ago, alacant said:

Hi

- Set the lens against the infinity stop and loosen the 3 grub screws holding the focus grip to the helicoid. Twist the grip so that after re-tightening the screws, you can now focus beyond infinity.

- The Bhatinov will give you focus on the red. The trick is to 'infinity' focus on a bright star until red fringing is seen. Now twist way from infinity so that the red just disappears. If it starts to go blue, you've gone too far. That's the best compromise I get with the 200/4 @ f 5.6. If you have time, f8 and smaller will allow you to focus 'normally' at infinity, but then it's painfully slow.

- fit an ir cut filter.

HTH.

Thanks. I'll try this.

4 hours ago, Knight of Clear Skies said:

Alternatively it could be some kind of internal reflection in the lens, possibly a problem with the coatings. There were applied to the lens 50 odd years ago and who knows what's been done to them since (an overzealous cleaner might have worn them away).

I'd recommend trying the camera with an auto-focus lens to confirm there isn't a problem there. You could also try the Takumar on a distant target in daylight, or on the Moon.

The camera does seem to be fine with my cheap 50mm.

I got this photo with the Takumar before I tried it for astro. Not a great photo, but no obvious problems. Nonetheless, a problem with internal reflection sounds plausible. Will have to get another, if true. At least they're cheap.

Just now, happy-kat said:

To clarify is your camera full spectrum modified?

My understanding is if it is there needs to be a UV/IR filter otherwise stars bloat. Whether the bloating shows on all stars or just the bigger ones I'm not sure.

No, it's only had it's hot mirror removed. It still has its LP1 filter, which blocks UV/IR.

Yeah, it seems to be interacting poorly with all wavelengths.

1 minute ago, happy-kat said:

Could you add them as jpg please, or instead are the separate channels all ok with good stars?

Green and blue look bad. Red is the same.

3 hours ago, happy-kat said:

If you split an image into the three separate colour channels, are the green and blue channels focused and good stars? Or are they all off.

Not sure if that will help much but it was a curious thought.

Here's the blue channel from one of the subs:

https://imgur.com/a/AxvNJDq

And the green:

https://imgur.com/a/36WQW33

Stars look the same, I'd say.

Taking a close look at my lens, I noticed what looks like a chip or aberration near the centre of one of the elements behind the objective. Look problematic?

10 minutes ago, rnobleeddy said:

 

This does look worse than others I've seen, but have you see other people with the same lens posting pictures? Do you know that lens is good for this kind of photography? 

Next thing I'd do is try a different lens. Or adapter. I rate https://www.amazon.co.uk/Pixco-Confirm-Adapter-Camera-M42-EOS/dp/B079BGLP4P?th=1 a lot more highly than the one I got for £3 on eBay, but they produced the same results.

Yeah, here's a review of the lens showing a pic taken with it:

http://www.nightofmanywords.com/articles/budget-lenses-for-astrophotography

And images on astrobin:

https://www.astrobin.com/search/?q=smc+takumar+200mm

A video extolling it's virtues:

https://www.youtube.com/watch?v=z6TuOa3mCFY

None have stars like mine.

9 minutes ago, happy-kat said:

I think there may have been careful use of focus to not focus on what would be perfect focus but just off focus so chromatic aberration was not at it's strongest. You'll have to fiddle and experiment.

I suppose I will. I also found this thread, where a user says that an M42 adaptor with a flange that presses the auto pin (such as mine) causes the lens to sit tilted on the camera:

Anyone know if that's right? Might it have any bearing on my problem?

2 minutes ago, ollypenrice said:

In support of this observation the 'shuttlecock' artifacts are predominantly red, suggesting that the lens is not controlling those newly active deep red wavelengths. Note that the shuttlecocks are all orientated as if racing away from a roughly central point, strongly suggesting an origin in the lens.

Origin

I echo the above sentiment. I've seem images taken with modified DSLRs and this lens and the stars don't look like mine.  Here is a review of the lens showing an image taken with it and a modded Canon DSLR, for example:

http://www.nightofmanywords.com/articles/budget-lenses-for-astrophotography

So, I don't know why the problem would apply only to me.

1 hour ago, rnobleeddy said:

I saw issues like this, but not as pronounced, using a few cheaper lenses with an astromodded camera. 

I never really figured out exactly why but it doesn't happen with a scope, it got better as I stopped down and it was worse on a camera with a full astromod compared to a stock camera.

The lens I was using had a red dot indicating the infinity IR focal position and that was quite a long way from standard infinity focus. I guessed I was getting some aberration on the red end which was exacerbated by the mod (although I was using a CLS CCD filter as well). 

 

I've seem images taken with modified DSLRs and this lens at the same f stop with stars that look nothing like mine. So I don't know why the problem would apply to me and not to them.

14 minutes ago, ollypenrice said:

It looks like a miscollimated lens to me, at first sight.

Olly

Could the adapter be the issue? It causing the lens to no sit perfectly flush with the camera body? It's just a cheap thing off Amazon.

I really hope that's not the case, as I can't afford a telescope. I've seem images taken with modified DSLRs and this lens at the same f stop with stars that look nothing like mine. So I don't know why the problem would apply to me and not to them.

Its hot mirror was removed by Juan from Cheap Astrophotography. 

I haven't yet, but I will when the clouds clear again.