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APO for skyguider pro + fuji x-t20


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Hi, I'm very new to this but I'm really loving astrophotography despite living in a very light polluted region without any chance of finding dark skies. I do have an unmodified Fuji X-T20 (APS-C XTrans sensor), an skyguider pro and a humble Samyang 12mm + nisi light pollution filter.

To capture deep sky objects I was considering to buy an small APO I can use with my skyguider pro and my x-t20.

I was pondering between WO Z61 and WO star 71-ii and a 2" IDAS filter. suggestions?

also, would it make sense to get an IDAS for my 12mm replacing the NISI? milky way with foreground on parks on this polluted town (Brighton, UK)

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I also have the Skyguider Pro. I had my eye on the WO71 you mentioned as well as the WO GT81. I've also got my eye on the Sky-watcher ProED 80. Right now I'm just using a DSLR camera and lenses until I pull the trigger. I'm interested to see what others recommend.

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Once you increase your resolution by using a much longer focal length you're going to find you need vastly higher tracking accuracy. I see the Skyguider has an ST4 guiding port. Were you thinking of guiding? I'm just wondering if you might not be better off moving up to a somewhat longer lens without going all the way to the 300-ish mm of the little Apos.

Olly

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6 hours ago, ollypenrice said:

I see the Skyguider has an ST4 guiding port. Were you thinking of guiding?

the idea was in my mind indeed. the star71 comes with rings to mount a guider while the z61 seems too small for that. do you think it would be cost effective to spend on the star71-ii and a guider kit for this "lightweight" setup? recommendations?

 

6 hours ago, ollypenrice said:

I'm just wondering if you might not be better off moving up to a somewhat longer lens without going all the way to the 300-ish mm of the little Apos.

you mean a telephoto lens? I thought they where incompatible with deep sky photography despite the focal length. too many elements, etc.

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9 hours ago, Buzzard75 said:

I also have the Skyguider Pro. I had my eye on the WO71 you mentioned as well as the WO GT81. I've also got my eye on the Sky-watcher ProED 80. Right now I'm just using a DSLR camera and lenses until I pull the trigger. I'm interested to see what others recommend.

aren't those too heavy for the skyguider pro? also, you have three completely different focal lengths there. what's a good focal length for a beginner like me? for easy targets that give good satisfaction while learning.

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9 hours ago, Alejandro M said:

the idea was in my mind indeed. the star71 comes with rings to mount a guider while the z61 seems too small for that. do you think it would be cost effective to spend on the star71-ii and a guider kit for this "lightweight" setup? recommendations?

 

you mean a telephoto lens? I thought they where incompatible with deep sky photography despite the focal length. too many elements, etc.

No, telephotos are not the best idea because of the multiple elements, as you say. Many people just use prime lenses (fixed focal length) of various focal lengths. I don't know what's available for your camera but if you can find the right adapters older primes are often a real bargain. You just won't have autofocus, which is fine anyway.

Olly

 

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9 minutes ago, ollypenrice said:

No, telephotos are not the best idea because of the multiple elements, as you say. Many people just use prime lenses (fixed focal length) of various focal lengths.

I think the terminology has gone a bit off-track here. Just to put the record straight (I'm a bit an*l about things like that :smile:), a telephoto lens is a lens which magnifies the image from the 'standard' focal length. They contain many elements these days, though zoom lenses generally have far more than prime lenses.

Ian

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4 minutes ago, The Admiral said:

I think the terminology has gone a bit off-track here. Just to put the record straight (I'm a bit an*l about things like that :smile:), a telephoto lens is a lens which magnifies the image from the 'standard' focal length. They contain many elements these days, though zoom lenses generally have far more than prime lenses.

Ian

Yes, we should be distinguishing between 'zoom' and 'prime' in this context.

Olly

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22 hours ago, Alejandro M said:

I do have an unmodified Fuji X-T20 (APS-C XTrans sensor)

Welcome Alejandro. I too use an X-Trans sensor camera, and if my X-T1 is anything to go by, it has a good red response for picking up Hydrogen-α. One point worth noting though, is that when you come to stack frames, which you will need to with DSO imaging, you will probably find that DSS won't work with them without first having to convert to .dng using the free Adobe DNG Converter, because of the unusual filter array. To avoid that I use AstroArt which works without conversion. However, when I say 'work' it does give a reasonable result but the processing isn't quite as it should be.

Cheers, Ian

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I found a 200mm f/3.5 rokinon prime for MD on ebay for £65 and I couldn't resist ? despite not been able to find any extra details or review. I guess this is what you were suggesting to get started. thanks!

do I want an empty adapter or an actual reducer with glass on it?

the questions about the small APO refractor, guiding and, filter are still open ?

 

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2 hours ago, ollypenrice said:

200mm is a nice FL for a huge number of targets. 

Olly

Agreed, given the very limited opportunities for AP I seem to get these days I've settled on the old Nikkor ED180 as my go to glass. Coupled with the 4/3rds sensors in my cameras (QHY9 and 163) the 180mm FL has a FOV (5.77° x 4.36°) that matches some classic DSO targets very well - NGC7822, IC1396, Sh2-129, Cygnus Loop, Orion's Sword etc.

Here's my "one plug" dual rig that I pretty much use exclusively now for HA work. I run it at f/3.46 with 72-52mm step down rings.

Dual-Rig-RLD.thumb.jpg.151816e214114e281df1054339743177.jpg

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7 hours ago, Alejandro M said:

I found a 200mm f/3.5 rokinon prime for MD on ebay for £65 and I couldn't resist ? despite not been able to find any extra details or review. I guess this is what you were suggesting to get started. thanks!

do I want an empty adapter or an actual reducer with glass on it?

If I understand your post correctly that's a Minolta Rokkor lens you've bought? If so, adapters are quite easy to come by for Fuji. The one in the following link allows infinity focus:

https://www.kentfaith.com/KF06.060_minolta-md-to-fuji-x-mount-adapter?cur=gbp&gclid=EAIaIQobChMIyPyYwOmc3QIVgbTtCh3HWQG3EAQYASABEgK5jPD_BwE

I'd definitely recommend using a lens collar of some type for mounting purposes, these lenses are quite weighty IIRC.

HTH

Rich 

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1 hour ago, RichLD said:

If I understand your post correctly that's a Minolta Rokkor lens you've bought? If so, adapters are quite easy to come by for Fuji. The one in the following link allows infinity focus:

https://www.kentfaith.com/KF06.060_minolta-md-to-fuji-x-mount-adapter?cur=gbp&gclid=EAIaIQobChMIyPyYwOmc3QIVgbTtCh3HWQG3EAQYASABEgK5jPD_BwE

on the pictures the product I bought has an adapter labeled MD-4/3 so I was indeed going to buy the exact K&F MD-FX on your link unless people recommended the usage of the reducer.. which I doubt because it adds cheap glass to my pictures

as the recommendation clearly went toward using a prime telephoto instead of an small refractor I was also considering buying a samyang 135mm f2 ED if this rokinon sucks

1 hour ago, RichLD said:

I'd definitely recommend using a lens collar of some type for mounting purposes, these lenses are quite weighty IIRC.

do you know any universal-ish lens support I could use? all those I've seen state very specific lens models or costs hundreds

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7 minutes ago, Alejandro M said:

do you know any universal-ish lens support I could use? all those I've seen state very specific lens models or costs hundreds

Lots of people have luck with pipe clamps such as the ones in the following link. A couple of these bolted to a dovetail should see you right ?

https://www.ebay.co.uk/itm/Rubber-Lined-Munsen-Ring-optional-MALE-Backplate-Pipe-Hanger-Clamp-Bracket/153000727776?hash=item239f8dd4e0:m:mzC80UWe8p6N4HhVW6J3jnQ

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3 hours ago, RichLD said:

I've settled on the old Nikkor ED180 as my go to glass

it looks like a very interesting option indeed. how do you mount it? I can't imagine your chopping board on a tripod ?

are those guider rings and dew heaters?

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Just now, Alejandro M said:

it looks like a very interesting option indeed. how do you mount it? I can't imagine your chopping board on a tripod ?

On one of these, with one of these to collimate the optics. The chopping board was to protect the table ??

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5 hours ago, Alejandro M said:

does anyone have experience with this kind of "collar" for DSLR + prime-telephoto astrophotography?

I would have thought it wouldn't work so well at odd angles. Something like this might be better.

https://www.teleskop-express.de/shop/product_info.php/info/p9891_TS-Optics-Telephoto-Lens-and-Camera-holder-with-Vixen-style-dovetail-bar.html. Steve Nickolls uses one successfully.

Ian

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6 hours ago, The Admiral said:

I would have thought it wouldn't work so well at odd angles. Something like this might be better.

https://www.teleskop-express.de/shop/product_info.php/info/p9891_TS-Optics-Telephoto-Lens-and-Camera-holder-with-Vixen-style-dovetail-bar.html. Steve Nickolls uses one successfully.

Ian

very fair point, I could use a velcro tie to keep it tight when hanging from the skyguider pro... but I guess it's time to start thinking like an astrophotographer and embrace the tube rings and dovetails ?

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  • 2 weeks later...

Hi Alejandro,

I'm also using a similar setup (Skyguider Pro and Fuji X-T1), and had the same questions as you. After a lot of research, I believe putting an actual telescope like those you mentioned would be pushing the mount. The limit, from what I've read here and here, appears more or less to be the WO 61 (there's a review on Astrobackyard). Over this weight/focal length, you will get much better results with a "real" EQ mount.

It's perfectly fine to use camera lenses instead of a telescope. The difference is that they were not tailored for astronomy/-photography, so they might have more distortions or aberrations. But some lenses are actually excellent performers. Also, by using a smaller aperture, you generally reduce the aberrations significantly.

If you want to do DSO with your X-T20 and SkyGuider, I think anything in the range 100-400 would be just fine. The good news is that you can adapt almost any lens ever made to your Fuji camera, using adapters. And there are lots of options, for all budgets ;)

Here are the lenses I'm using and can recommend:

- Canon 300mm f/4L (non IS) (+/- 1.4x teleconverter, which makes it a 420mm f/5.6 lens)

- Pentax Super Takumar 200mm f/4 (very cheap)

- Samyang 135mm f/2 (probably the best astro lens out there, and it comes in Fuji mount)

Here are some adaptable lenses that are often used by astrophotographers with great success:

- Canon 200mm f/2.8L

- Nikon 180mm f/2.8

- Canon 400mm f/5.6L

- Samyang/Rokinon 85mm f/1.4

- Canon 100-400 f/4.5-5.6 (yes, a zoom lens!)

- Check out this article for more recommendations!

If I could recommend only one, it would be the Samyang 135mm f/2. You can't go wrong with this lens, and though the focal length isn't that long, it's decent enough for a lot of targets. The 24 mpix of your X-T20 will allow you to crop if needed. Also, the wider aperture allows faster shutter speeds, which can be forgiving when getting started with a mount. The image quality is excellent, especially around f/2.8-f/3.5.

Also, the 135mm from Samyang can be used with a lens collar (only the Fuji and Sony version, on which the back of the lens acts as a spacer. Nikon/Canon version don't have this spacer). There's no collar, as far as I know, that fits the back of the lens perfectly, but with a bit of tape, it works just fine :)

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Regarding your question about filters: no, an IDAS filter (assuming you're talking about the LPS) would not work on a 12mm lens (assuming the Samyang f/2). These filters are meant to be used with telescopes, or telephoto lenses. So anything > 100mm, if I remember correctly. On a wide angle lens, it will not work.

For wide angle, you can still use didymium filters, like the Hoya RA54 Red Enhancer.

Good luck! :)

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