Mirror lens

[TiffsAndAstro]

So I have a very cheap mirror lens I bought mostly for the T2 canon adapter.

In daylight I quite like it.

For astrophotography it's rubbish. However, it looks vaguely like a mini  maksutof so I want it to be amazing ;(

When I do manage to vaguely focus it, he stars look a  square/cross shaped. Is it even worth me considering removing the central obstruction and could I only adjust it at night on stars?

Or should I just chuck it in the bin?

This image was some time ago, about 45 mins total integration time and rubbish.

 

[Vroobel]

I would like to see it after a BlurXterminator process in Pixinsight. Could you please share it somewhere uncompressed and in a highest size?

[TiffsAndAstro]

33 minutes ago, Vroobel said:

I would like to see it after a BlurXterminator process in Pixinsight. Could you please share it somewhere uncompressed and in a highest size?

Er no, sorry they were deleted to save disk space a month ago.

I don't have pix insight anyway.

Not sure it was cropped either. Also it's the bestest image I managed with my minimak

[Vroobel]

12 minutes ago, TiffsAndAstro said:

. don't have pix insight anyway.

While I have it. 

[Elp]

Cross shape could be astigmatism, is there a way to collimate a very far off maybe?

[TiffsAndAstro]

7 minutes ago, Elp said:

Cross shape could be astigmatism, is there a way to collimate a very far off maybe?

Pretty sure you're spot on, and i think there's some adjustment available if i pop the cap on the central obstruction.

thing is, i rather like its daylight performance. its a pain to focus, and a remote shutter release is required as it shakes more than shaking stevens going before a judge. however i wouldn't want to risk knackering its daylight performance to tinker with unrealistic expectations. 

i can't find much on the interwebs about adjusting a mirror lens, so i wondered if i could look at stuff on how a mak-cass (i assume it imitates) and have a try based on that?

[Elp]

Not sure without looking at one in hand. From what I've read they're not suited to astro at all, but then again a lot of lenses aren't.

[happy-kat]

That image isn't bad, the star shapes are quite good so if that was the lens I had I'd be trying it again. 

If it's a mirror lens is it f8? Whilst that might be slower then F5 still useable on bright targets could also try it on bright globular clusters

I get odd white cross shape stars and think it's more the camera then the lens 

As processing skills develop old data can be revisited and reprocesses.

If you decide you don't want it, clean it and could pass it to a charity shop 

[TiffsAndAstro]

50 minutes ago, happy-kat said:

That image isn't bad, the star shapes are quite good so if that was the lens I had I'd be trying it again. 

If it's a mirror lens is it f8? Whilst that might be slower then F5 still useable on bright targets could also try it on bright globular clusters

I get odd white cross shape stars and think it's more the camera then the lens 

As processing skills develop old data can be revisited and reprocesses.

If you decide you don't want it, clean it and could pass it to a charity shop 

I still think its a decent lens for daylight - small, very light and cheap yeah its f8 and darker than my bias frames  for astro anyway. 

Ill do as you say when i get a bit bored of my 72ed. gonna try the bahtinov mask from my 72ed on it - what could go wrong?

btw i also thought i might have camera/sensor alignment issue because of those shapes, but after getting my 72ed, i think it was more of a vintage lens issue  well, hopefully

its ok for the moon btw, so maybe i should keep it for luna photography, which i never do?

Edited April 16 by TiffsAndAstro

[TiffsAndAstro]

2 hours ago, Vroobel said:

While I have it. 

Sorry I misunderstood I'd love you to have a go. I'll check my SD cards, possible they are on there.

 

[TiffsAndAstro]

I'm seriously looking at a nas server thing with spinning metal disks for storage.

I massively underestimated data storage requirements. I'm crap and noob and even I regret deleting stuff.

My plan is to have cern begging me to let them have a little of my server storage

[Vroobel]

I can recommend this, if you are familiar with IT, Linux, Raspberry Pi etc. :

https://pimylifeup.com/raspberry-pi-openmediavault/

I use it with a USB 3.0 12TB WD Black HDD with real pleasure. Factory-made solutions are OK, but they are much more expensive. 

[TiffsAndAstro]

Just now, Vroobel said:

I can recommend this, if you are familiar with IT, Linux, Raspberry Pi etc. :

https://pimylifeup.com/raspberry-pi-openmediavault/

I use it with a USB 3.0 12TB WD Black HDD with real pleasure. Factory-made solutions are OK, but they are much more expensive. 

I'm ok with that stuff but mainly because I can watch a video or read a post and follow instructions.

Coincidentally I was looking at a 4gb pi4 to flash astroberry on. Never done it, but it doesn't seem to be rocket surgery. Your link would mean I could do both but with only 1.5x the effort

I like the neatness cable management of the asi air, but I also like Nina and chrome remote desktop works a charm. So maybe a nano windows pc on my scope and the pi4 server for my storage.

[Vroobel]

The ASIAir is OK if you consider simple ZWO-only equipment. Leave the idea if you aren't ready for it. The NINA is powerful and have a lot of features not existing (yet?) in the ASIAir which work with everything. 

[TiffsAndAstro]

7 minutes ago, Vroobel said:

The ASIAir is OK if you consider simple ZWO-only equipment. Leave the idea if you aren't ready for it. The NINA is powerful and have a lot of features not existing (yet?) in the ASIAir which work with everything. 

i really dislike manufacturer lock in. but i have a macbook. running nina etc on boot camp. im in no hurry and can wait try and find a cheap light 2/4core windows pc to velcro onto the scope. 

the pi for a server is a great option though. 

right after that, ill make a pier made out of stacked baked bean cans and string  

Edited April 16 by TiffsAndAstro

[Vroobel]

Remember that the NAS also may break. The proper backup should follow a rule of 3-2-1: 3 different backups, placed in 2 different locations, at least 1 offline (e.g. detachable USB). 

[TiffsAndAstro]

38 minutes ago, Vroobel said:

Remember that the NAS also may break. The proper backup should follow a rule of 3-2-1: 3 different backups, placed in 2 different locations, at least 1 offline (e.g. detachable USB). 

One needs to be inside a firesafe though, surely?

I'm hoping cheap flash drives and hurling them into distant neighbours gardens will suffice.

[Vroobel]

Of course, not. That's theory.

[TiffsAndAstro]

17 hours ago, Vroobel said:

While I have it. 

Ok had a search through both cards and nothing, sorry

if its clear this evening i can try imaging with it again, but not in orion too low for me to see now

[TiffsAndAstro]

17 hours ago, Vroobel said:

Of course, not. That's theory.

So It may might be clear tonight and I'm scopeless.

Except for my mighty minimak astrograph, of course

So, as you're forcing me to, and for the good of science in general I might set up and use my mirror lens so I can swear and not focus it for two hours. I'll even try the bahtinov from my 72ed. How bad can it be?

If I manage to do that, and hang my guider off the front of the vixen dovetail, what should I point it at? Orion way too low

 

Edited April 17 by TiffsAndAstro

[Vroobel]

What is it's focal length? 

Try M81 and M82, they are always visible. 

[TiffsAndAstro]

2 minutes ago, Vroobel said:

What is it's focal length? 

Try M81 and M82, they are always visible. 

Will give it a go if it's clear not too windy.

Maybe m101 also

[Vroobel]

Use dithering, if the setup is undersampling, I'll try drizzling x2. 

[Vroobel]

16 minutes ago, Vroobel said:

Use dithering, if the setup is undersampling, I'll try drizzling x2. 

Haha, my mistake. You will stack it, so do whatever you want. 🤪 I know that you have problems with drizzle, so let's leave this idea. 

[TiffsAndAstro]

7 hours ago, Vroobel said:

Haha, my mistake. You will stack it, so do whatever you want. 🤪 I know that you have problems with drizzle, so let's leave this idea. 

i couldn't attach my guidescope for want of a second screw. i use my only screw to hold the camera to the dovetail  

i tried to image m86 (cos i thought you asked for that not m81 and m82 lol) but i had meridian flip checked and on centering it would flip flop - sending the mount from one extreme to another, so i thought i'd leave it for now and come back to it later.

so im doing m101 for maybe 2 hours unguided 120s subs at iso800

right after that ill do m81 m82

focusing was a *&*&^^ &^")(*    "q(*"(*&£(&*^*£  excuse my french. i used the bahtinov from my 72ed, got it pretty much perfect then took test shot. stars were terrible. so i focused them by eye/hfr. 4.5 ish was the best i could manage. 

even with this recalcitrant b£$%^$d of a lens, 3ppa with nina is a dream. didn't even take the caps of my mount's polar scope.  8" total error in pa in about 15 mins

 

Popped to the shop decided to use chrome remote desktop on my phone to check any problems. Everything seems good but hfr getting worse and I CBA trying to refocus

I might just leave it on m101 see what happens

Edited April 17 by TiffsAndAstro