I ditched my ED refractor for a vintage lens

[Chris]

Despite many years of dabbling, I still class myself as a noob when it comes to DSO imaging. Well maybe another way of looking at it is that I tend to keep things simple and affordable i.e. just some basic star tracker antics with a stock Fuji camera for example. However, It's surprising how much can actually still go wrong even when keeping things simple!

For starters my eyes were bigger than my belly trying to image unguided with a 72mm refractor with 432mm focal length on a star tracker but I knew this going in. Does anyone else try things they know aren't a good idea? 

Much better to stick to something like a Redcat51 or an 8 quid 200mm vintage lens in this case. 

 

   

[Dazzyt66]

15 hours ago, Chris said:

Despite many years of dabbling, I still class myself as a noob when it comes to DSO imaging. Well maybe another way of looking at it is that I tend to keep things simple and affordable i.e. just some basic star tracker antics with a stock Fuji camera for example. However, It's surprising how much can actually still go wrong even when keeping things simple!

For starters my eyes were bigger than my belly trying to image unguided with a 72mm refractor with 432mm focal length on a star tracker but I knew this going in. Does anyone else try things they know aren't a good idea? 

Much better to stick to something like a Redcat51 or an 8 quid 200mm vintage lens in this case. 

 

   

I've had a similar epiphany regarding vintage lenses - here's 50 mins of M31 captured last night and quickly stacked and processed this morning. Using a 200mm f3.5 lens from ebay (£20) plus my modded 1100D I also got from eBay for £60 a few years ago and had it modded recently. I do use my HEQ5 (which is total overkill) but I'm more than happy with the images I'm able to get from my Bortle 7 garden  

[Chris]

Good job! Was this shot wide open at f/3.5? I reckon you can clean those corner stars up by stopping down a little bit. I ended up stopping down to f5.6 which did the trick.

M31 does look well framed at 200mm so I'm looking forward to giving this one a go. I've only ever imaged it with an ED66 which is slightly on the tight side.   

[Dazzyt66]

22 minutes ago, Chris said:

Good job! Was this shot wide open at f/3.5? I reckon you can clean those corner stars up by stopping down a little bit. I ended up stopping down to f5.6 which did the trick.

M31 does look well framed at 200mm so I'm looking forward to giving this one a go. I've only ever imaged it with an ED66 which is slightly on the tight side.   

Thanks! Yeah, fixed 200mm Kalimar lens wide open at 3.5. I wanted to grab as much info as I could in shortest time given the weather unpredictability. As this is only my 3rd 'real' attempt at imaging and processing I'm chuffed with it  

[Whistlin Bob]

I've enjoyed several of your videos Chris, and this is another good one 👍. Mucking about with vintage lenses on a Star Adventurer had become a bit of a side hobby for me over the last couple of years- by co-incidence one of them is a 200mm Chinon that I thought was a steal at £15- clearly I should have spoken to you! I've also found it works better by stopping down a bit as wide open it can't bring all the colours to focus. Alternatively it works pretty well wide open with narrowband filters- see below rgb and ha efforts on M42.

[Rustang]

Just started messing around with this basic type of astrophotography myself

I find the simplicity of it refreshing 😊

Cygnus at 28mm 

 

[Whistlin Bob]

1 hour ago, Rustang said:

Cygnus at 28mm 

Love it! ... and at 50mm with a small sensor

... plus a bit of Cepheus

 

[rnobleeddy]

Awesome stuff.

I picked up an F/4.5 300mm Photosniper lens on ebay (tair-3-phs) a while back and just got it prepared for the next clear night. 

My previous attempts with vintage lens always lead to disappointment in the end but I have high hopes for this one!

 

 

[Rustang]

43 minutes ago, rnobleeddy said:

Awesome stuff.

I picked up an F/4.5 300mm Photosniper lens on ebay (tair-3-phs) a while back and just got it prepared for the next clear night. 

My previous attempts with vintage lens always lead to disappointment in the end but I have high hopes for this one!

 

 

Yeah they can be hit and miss, my Pentax Takumar 135 f3.5 is the best one I've brought so far, probably should have brought 28mm version of that lens instead of the Hoya but they are cheap enough to swop about. 

[happy-kat]

I like the tackumar 50mm f2 I have and now that I can fit 1.25 filters to the canon 1100d it opens up other possibilities. For longer reach as the vintage nikon 200mm I have needs too much stopping down f8 I'll use the evoguide with evoffv2 ff.

[Chris]

4 hours ago, Whistlin Bob said:

I've enjoyed several of your videos Chris, and this is another good one 👍. Mucking about with vintage lenses on a Star Adventurer had become a bit of a side hobby for me over the last couple of years- by co-incidence one of them is a 200mm Chinon that I thought was a steal at £15- clearly I should have spoken to you! I've also found it works better by stopping down a bit as wide open it can't bring all the colours to focus. Alternatively it works pretty well wide open with narrowband filters- see below rgb and ha efforts on M42.

That's good to hear, thank you   Ha yeah I kept dropping the price out of curiosity but it was getting a tad bit silly by the time it had dropped to 8 quid. Glad I held onto it now despite the lens having more lateral chromatic aberration than you can shake a stick at! When you pixel peep the corner stars, the blue channel sits besides the star it's meant to be apart of lol 

Great work in narrowband there! 

[Chris]

4 hours ago, Rustang said:

I find the simplicity of it refreshing 😊

Cygnus at 28mm 

Me too. It's not my first rodeo with vintage lens astrophotography as I've dabbled a bit here and there, but it really is relatively easy and cheap! 

Great wide angle Cygnus by the way. looking at it I think 50mm might be good for capturing both NGC7000 and Sadr. I might give that a go. 

 

[Chris]

2 hours ago, Rustang said:

Yeah they can be hit and miss, my Pentax Takumar 135 f3.5 is the best one I've brought so far, probably should have brought 28mm version of that lens instead of the Hoya but they are cheap enough to swop about. 

I have that very same 135mm on my rig at the moment, it's great!

[vlaiv]

22 hours ago, Chris said:

For starters my eyes were bigger than my belly trying to image unguided with a 72mm refractor with 432mm focal length on a star tracker but I knew this going in. Does anyone else try things they know aren't a good idea? 

If your 200mm lens can go unguided - I don't see why your 432mm refractor can't be used unguided as well?

Just because something has 432mm of FL - you don't need to use it as 432mm of FL. You can use it as 144mm FL for example.

Lens have advantage that they are simpler to use (that is actually questionable - not sure how simple focusing is for example, or mounting of the lens and getting spacing right - maybe on DSLR, but not on astro camera), but have disadvantage of having optics that is not diffraction limited.

Scope has "disadvantage" of being "long focal length" - but in reality, that is not disadvantage - it is simply use case scenario.

What prevents you from taking your 432mm FL scope and making 3x3 panel mosaic with each mosaic pane being binned x3.

Result will be almost the same as using 144mm FL lens (differences will be that telescope image will be diffraction limited and that you'll get slightly smaller FOV due to overlap needed to stitch mosaic). Processing is a bit more involved, but result is the same resolution as using 144mm lens.

If you can use 200mm lens unguided - why wouldn't it work for 144mm FL?

[rnobleeddy]

1 hour ago, vlaiv said:

If your 200mm lens can go unguided - I don't see why your 432mm refractor can't be used unguided as well?

Just because something has 432mm of FL - you don't need to use it as 432mm of FL. You can use it as 144mm FL for example.

Lens have advantage that they are simpler to use (that is actually questionable - not sure how simple focusing is for example, or mounting of the lens and getting spacing right - maybe on DSLR, but not on astro camera), but have disadvantage of having optics that is not diffraction limited.

Scope has "disadvantage" of being "long focal length" - but in reality, that is not disadvantage - it is simply use case scenario.

What prevents you from taking your 432mm FL scope and making 3x3 panel mosaic with each mosaic pane being binned x3.

Result will be almost the same as using 144mm FL lens (differences will be that telescope image will be diffraction limited and that you'll get slightly smaller FOV due to overlap needed to stitch mosaic). Processing is a bit more involved, but result is the same resolution as using 144mm lens.

If you can use 200mm lens unguided - why wouldn't it work for 144mm FL?

I guess from my experience, there's a lot more to go wrong during acquisition, but I'd also argue that processing is quite a lot more involved. I'm not aware of any free/cheap software that makes this easy? 

[Chris]

2 hours ago, vlaiv said:

If your 200mm lens can go unguided - I don't see why your 432mm refractor can't be used unguided as well?

Just because something has 432mm of FL - you don't need to use it as 432mm of FL. You can use it as 144mm FL for example.

Lens have advantage that they are simpler to use (that is actually questionable - not sure how simple focusing is for example, or mounting of the lens and getting spacing right - maybe on DSLR, but not on astro camera), but have disadvantage of having optics that is not diffraction limited.

Scope has "disadvantage" of being "long focal length" - but in reality, that is not disadvantage - it is simply use case scenario.

What prevents you from taking your 432mm FL scope and making 3x3 panel mosaic with each mosaic pane being binned x3.

Result will be almost the same as using 144mm FL lens (differences will be that telescope image will be diffraction limited and that you'll get slightly smaller FOV due to overlap needed to stitch mosaic). Processing is a bit more involved, but result is the same resolution as using 144mm lens.

If you can use 200mm lens unguided - why wouldn't it work for 144mm FL?

I think this would only work if you could easily bin mirrorless and DLSR pixels, and if you also had the inclination to do a mosaic. 

I would personally just use a wider lens to increase the pixel scale and in turn how long you can track without smearing the photons across pixels on the sensor. 

Lenses can be stopped down to help even budget lenses perform a little better, but you get what you pay for with both lenses and telescopes of course. 

The mounting point is often on the base of the camera when using vintage lenses, so off axis weight on declination can be a problem, although I do personally prefer the helical focuser of lenses as they don't slip like my Crayford did when pointed close to zenith.... despite being locked off .  I also had problems with the refractor almost hitting the tripod, and the balance was very tricky on dec also with the ED72, reducer/flattener and camera hanging off the back. 

I do think you could do as you say with a dedicated astro cam with binning and mosaics, but I will hazard a guess that most people using star trackers are either relatively new to imaging or just want to keep things simple.

I think I get your point, it's about pixel scale ultimately rather than focal length, but for a given 'fixed' pixel size focal length does then of course matter.

 

 

 

 

 

 

 

 

 

 

Edited September 12, 2021 by Chris

[vlaiv]

1 hour ago, rnobleeddy said:

I guess from my experience, there's a lot more to go wrong during acquisition, but I'd also argue that processing is quite a lot more involved. I'm not aware of any free/cheap software that makes this easy? 

Yes, it is a bit of a pain to process mosaics, but as far as I know AstroPixelProcessor is capable of doing that almost automatically (although it is not free of course)?

As alternative - ImageJ / Fiji (distribution loaded with plugins) has everything you need to bin / stitch / process your mosaic images.

Here is an image I did like that (ImageJ) with small sensor (ASI185) and achromatic refractor (ST102):

Only thing missing to make this proper image is flats - but as it turns out - that is rather fortunate as it let us see the panels involved. This was done at F/7.5 with Wratten #8 filter to tame chromatic blur (and under heavy LP - so it did not go deep).

This FOV is equivalent of about 166mm (500/3) with that sensor.

1 hour ago, Chris said:

I think this would only work if you could easily bin mirrorless and DLSR pixels, and if you also had the inclination to do a mosaic. 

You are quite right that novice imagers will have tough time with everything involved, let alone doing mosaics, but I'm not seeing you as novice imager, but rather someone who likes to experiment (and this is nice project - do comparison: lens vs scope + mosaic).

In any case - binning of any CMOS data in software is a breeze (as long as your software supports that - it's nothing more than press of a button).

[Chris]

37 minutes ago, vlaiv said:

You are quite right that novice imagers will have tough time with everything involved, let alone doing mosaics, but I'm not seeing you as novice imager, but rather someone who likes to experiment (and this is nice project - do comparison: lens vs scope + mosaic).

I will certainly add it to my list of project/video ideas, vlaiv! I agree it would be interesting to see if there is anything the math doesn't reveal. I would need to change my software though as I currently use DSS and GIMP for DSO's.   

My very next project is to play around with smartphones for astrophotography. I've recently upgraded to a Samsung Galaxy 20 FE and it looks very promising using the pro photography mode which gives full manual control and RAW. I will be interested to see what can be done with that    

[Chris]

P.s. that's a very nice mosaic from the achromat, the CA certainly isn't quite as apparent at that scale! 

[vlaiv]

21 minutes ago, Chris said:

P.s. that's a very nice mosaic from the achromat, the CA certainly isn't quite as apparent at that scale! 

It is mainly due to stopped down aperture and filter used. I did a test back then to see what combination would work with ST102.

I ended up making 80mm, 66mm aperture masks (I think). In the end I chose 66mm based on that test:

Columns are just different level of stretch of the same star image, while rows are Mask and then Mask + Wratten #8 filter, so full aperture, full aperture + filter, 80mm, 80mm + filter, 66mm and in the end 50mm - scope cover small opening (which is about 2" in diameter).

I figured that 66mm + filter is virtually free of false color.

In the end, I made another image to see if I can go deeper - this time only 2x2 mosaic (I might have even used flats this time around):

[Chris]

20 minutes ago, vlaiv said:

It is mainly due to stopped down aperture and filter used. I did a test back then to see what combination would work with ST102.

I ended up making 80mm, 66mm aperture masks (I think). In the end I chose 66mm based on that test:

Columns are just different level of stretch of the same star image, while rows are Mask and then Mask + Wratten #8 filter, so full aperture, full aperture + filter, 80mm, 80mm + filter, 66mm and in the end 50mm - scope cover small opening (which is about 2" in diameter).

I figured that 66mm + filter is virtually free of false color.

In the end, I made another image to see if I can go deeper - this time only 2x2 mosaic (I might have even used flats this time around):

Brilliant vlaiv! 66mm even without the filter is a major improvement, and you're still at f7.5 which isn't that slow. 

This seems like a great option for budget imaging, just grab an ST80 or similar and stop it down a bit. I kind of want to try it myself. 

No pun intended but I 'figure' it also helps with the optical figure. The edge of the lenses is usually worst culprit from what I understand. 

 

 

 

[vlaiv]

Just now, Chris said:

Brilliant vlaiv! 66mm even without the filter is a major improvement, and you're still at f7.5 which isn't that slow. 

This seems like a great option for budget imaging, just grab an ST80 or similar and stop it down a bit. I kind of want to try it myself. 

No pun intended but I 'figure' it also helps with the optical figure. The edge of the lenses is usually worst culprit from what I understand. 

 

 

 

Yes, it helps with spherochromatism as well.

ST80 is one option, but there is even cheaper and lighter version:

https://www.firstlightoptics.com/startravel/skywatcher-mercury-705.html

Only problem is focuser. Putting something like DSLR on that thing (or ST80 / ST102) is asking for trouble . I used very light planetary type camera (drawback - small sensor).

Maybe mirrorless would be a good match? Those are a bit lighter than DSLR-s.

[Chris]

14 minutes ago, vlaiv said:

Yes, it helps with spherochromatism as well.

ST80 is one option, but there is even cheaper and lighter version:

https://www.firstlightoptics.com/startravel/skywatcher-mercury-705.html

Only problem is focuser. Putting something like DSLR on that thing (or ST80 / ST102) is asking for trouble . I used very light planetary type camera (drawback - small sensor).

Maybe mirrorless would be a good match? Those are a bit lighter than DSLR-s.

Yes some of the mirroless cameras weigh about the same as a diagonal and eyepiece. Also have you seen the new ZWO ASI485 and 482's Large sensor planetary cams 😎

https://www.firstlightoptics.com/zwo-cameras/zwo-asi-482mc-usb-30-colour-camera.html

https://www.firstlightoptics.com/zwo-cameras/zwo-asi-485mc-usb-30-colour-camera.html

 

[callisto]

11 hours ago, Rustang said:

Just started messing around with this basic type of astrophotography myself

I find the simplicity of it refreshing 😊

Cygnus at 28mm 

 

Excellent, I love these wide images, well done 

 

Mark

[vlaiv]

21 minutes ago, Chris said:

Yes some of the mirroless cameras weigh about the same as a diagonal and eyepiece. Also have you seen the new ZWO ASI485 and 482's Large sensor planetary cams 😎

https://www.firstlightoptics.com/zwo-cameras/zwo-asi-482mc-usb-30-colour-camera.html

https://www.firstlightoptics.com/zwo-cameras/zwo-asi-485mc-usb-30-colour-camera.html

 

Seen those, and not sure how to "classify" them yet.

ASI178mc - £8.21 per mm2

ASI485mc - £5.59 per mm2

ASI183mc - £4.46 per mm2

ASI294mc - £2.69 per mm2

All of those can do planetary as well as DSO imaging, and size of camera contributes to speed of system.

Just for DSO imaging - Canon M200 is hard to beat, about the same price as ASI482/485 - £398 at B&H - it costs £1.19 per mm2