Vixen VSD100 f3.8 5-element Apochromat

[Tim]

The scope has now been delivered, and is patiently waiting to be unboxed and set up. It will also be available for viewing at Astro fest this year.

What are the chances of some decent clear nights do we think?!?!

[gingergeek]

looking forward to the report but I feel the weather has other plans.

[steppenwolf]

That's exciting, Tim I shall watch this space with keen interest!

[AndyUK]

I'm also very much looking forward to seeing the results from this scope... (Not that I could ever afford to buy one though - In fact, I'm not sure I could even afford to buy the reducer!)

[michael.h.f.wilkinson]

A scope to drool for. Way outside my budget, however

[Naemeth]

I couldn't afford it now, but should the reviews be excellent I can see myself budgeting and saving for one for the future .

[Tim]

I now have the scope mounted and fitted with a camera to check spacings and so on, but no clear skies to get some images.

If the results are as nice as the fit and finish of the telescope then I might just have to sell off a couple of Kidneys and get one.

[AndyH]

No pics of your new treasure??

How very dare you sir !!

[ollypenrice]

This is an exciting scope in good hands. I'm keen on the Tak FSQ 106 but it is vulnerable in one key area; it is ultra-sensitive to fucus drift during temperature change and in many environments it isn't realistic to use the later ones without robotic focus between subs. The same appears to be true of the TeleVue NP101, though this is based only on one example I've seen. So, Vixen, have you cracked this problem? If so, you'll induce some disloyalty, maybe, from the Tak camp!

Tim, I hope you'll give it a spin in RGB because NB won't test the correction. You'll love the field with your Atik 11000. It just makes me chuckle every time a new target appears on the screen...

Olly

[Tim]

I haven't taken any pics Andy, for the simple reason that set up as it is, it looks Scruffy! Not the scope, it's a beauty, but the proper rings aren't available yet, so it is just in some scope rings, and to protect the body I have wrapped it in a protective layer.

The ability to hold focus is an interesting challenge, at f3. 8 the depth of acceptable focus is very shallow.

I plan to use my 11000, in ROB, the 460 ex OSC, and a DSLR. Would be nice to have a full frame DSLR to play with on it too

[gingergeek]

Maybe tonight Tim, looking clear here in Hampshire for the night. Coventry is not completely clear but may give enough time for a quick test.

Wishing you clear Skies !

[FLO]

This is a good day for enthusiasts of Japnaese-made refractors

The Vixen VSD100 f3.8 APO has arrived and is available for delivery in 2-3 working days. 

The price is £4,995 

Vixen tube-rings are scheduled to arrive May (the OTA diameter is 120mm) and the optically-matched reducer and extender will be available around summertime. 

For those who are new to this thread the Vixen VSD 100 is essentially an upgrade of the Pentax 4-element SD100 with an additional lens element and new lens coatings for a higher level of optical performance. The 5-element design is made from Japanese Ohara glass and includes an SD and ED element for very high colour correction. New lens coatings have been specially developed for the individual glass types.

The flat, evenly illuminated field will cover even 645 medium format sensors! 

A large precise helical focuser is also included. 

Tim Jardine has been loaned one for testing with his Atik 11000 camera but the weather hasn't been good and he needed to return it recently so it could be displayed at Astrofest . But weather permitting we should soon see some real-world results. 

[Naemeth]

This is a good day for enthusiasts of Japnaese-made refractors

The Vixen VSD100 f3.8 APO has arrived and is available for delivery in 2-3 working days. 

The price is £4,995 

Vixen tube-rings are scheduled to arrive May (the OTA diameter is 120mm) and the optically-matched reducer and extender will be available around summertime. 

For those who are new to this thread the Vixen VSD 100 is essentially an upgrade of the Pentax 4-element SD100 with an additional lens element and new lens coatings for a higher level of optical performance. The 5-element design is made from Japanese Ohara glass and includes an SD and ED element for very high colour correction. New lens coatings have been specially developed for the individual glass types.

The flat, evenly illuminated field will cover even 645 medium format sensors! 

A large precise helical focuser is also included. 

Tim Jardine has been loaned one for testing with his Atik 11000 camera but the weather hasn't been good and he needed to return it recently so it could be displayed at Astrofest . But weather permitting we should soon see some real-world results. 

Thanks for the automated email about it Steve . I'd better start saving soon even though it's about £1k less than I was expecting .

[Tim]

I have just received the review scope again, (it's been visiting Astrofest and other photography shows) complete with rings, so will recommence testing and reviewing very soon

The weather was appalling when I last tried the scope, in the middle of the floods, so let's hope for a better result this time round!

Also, The scope will be with me at SGL9, and hopefully in use, weather permitting. I may not be able to stay past the Friday though, so if you wish to see the scope in action please allow for that.

[Rossco72]

If my 6 numbers come up, this might be high on my list.....

Looks like it could be special.

[carlosgib]

Hi guys, any further news on the Vixen VSD100, i mean on the availability to purchase, if the proper rings are available, if the focal reducer has finally been produced and available, and finally has anyone tested the scope and any comparison to the  Takahashi FSQ 106ED  in terms of image quality.

Thanks

[FLO]

Hi guys, any further news on the Vixen VSD100, i mean on the availability to purchase, if the proper rings are available, if the focal reducer has finally been produced and available, and finally has anyone tested the scope and any comparison to the  Takahashi FSQ 106ED  in terms of image quality.

Tim had one on loan. He didn't have a lot of opportunity to use it (the weather didn't cooperate and it was needed for a magazine review) but when I spoke with him at SGL9 his conclusion was it had a marvellous flat field and excellent resolution but colour performance was very dependant on precise and critical focus, which is normal for an ultra-fast telescope of this type. A comparison with the FSQ106? The VSD100 is in short supply so I think it will be a while before we see a report from someone able to compare them. It will also be difficult to find someone truly neutral and objective, owners tend to promote and recommend whatever they have purchased (if you had just spent £5k on a telescope you probably would too). But both telescopes are expensive high-end Japanese-made astrographs so I expect their performance will be very similar. 

We should have an ETA for the tube-rings and reducer soon. 

HTH, 

Steve

[Earl]

I think a key issue with the scope is how well it holds focus over the night and also automated focus on filter change.

[Rodd]

On 09/08/2013 at 03:07, ollypenrice said:

F3 that just worked? Yes indeed!

Yes but as we are now so painfully aware, focal ratio without aperture is a meaningless number.  Likewise aperture without focal ratio--but it is a bit more meaningful with respect to speed (very meaningful with respect to resolution).  If aperture yields speed, my 11" F7 should be blazing (its not).  If a fast focal ratio yielded speed my FSQ at F3 would be blazing....its not. 

Rodd

[Adam J]

4 hours ago, Rodd said:

Yes but as we are now so painfully aware, focal ratio without aperture is a meaningless number.  Likewise aperture without focal ratio--but it is a bit more meaningful with respect to speed (very meaningful with respect to resolution).  If aperture yields speed, my 11" F7 should be blazing (its not).  If a fast focal ratio yielded speed my FSQ at F3 would be blazing....its not. 

Rodd

I am very confused by this statement Rodd, am not sure what your driving at.

[Rodd]

11 hours ago, Adam J said:

I am very confused by this statement Rodd, am not sure what your driving at.

Telescopes are not cameras.  Focal ratio is only relevant when one can alter aperture--as in cameras.  Changing a 5" refractor to F3 by adding a reducer does not really make the scope faster--as in shooting with a F3 Epsilon--Its the epsilons aperture that controls the speed.  People collect beautiful images in 1 night with epsilons.  I got the FSQ 106 and .6x reducer to do the same thinking that the focal ratio was going to provide this to me.  I was wrong--I still need 15-20 hours per image.  Will the FOV SNR be achieved faster than the FOV SNR when you add the reducer? n sure--but not like people think.  Making an F5 refractor F3 will not increase its speed by 4x (or whatever the anticipated value is).  Now add 5" of aperture while maintaining the F3 focal ratio  and the speed DOES increase.  You need focal ratio AND aperture in the equation.  Its the dreaded focal ratio myth.......it got me.

Rodd

[Adam J]

1 hour ago, Rodd said:

Telescopes are not cameras.  Focal ratio is only relevant when one can alter aperture--as in cameras.  Changing a 5" refractor to F3 by adding a reducer does not really make the scope faster--as in shooting with a F3 Epsilon--Its the epsilons aperture that controls the speed.  People collect beautiful images in 1 night with epsilons.  I got the FSQ 106 and .6x reducer to do the same thinking that the focal ratio was going to provide this to me.  I was wrong--I still need 15-20 hours per image.  Will the FOV SNR be achieved faster than the FOV SNR when you add the reducer? n sure--but not like people think.  Making an F5 refractor F3 will not increase its speed by 4x (or whatever the anticipated value is).  Now add 5" of aperture while maintaining the F3 focal ratio  and the speed DOES increase.  You need focal ratio AND aperture in the equation.  Its the dreaded focal ratio myth.......it got me.

Rodd

A reducer should increase your per pixel photon collection rate though, that can be mathematically demonstrated. The problem comes when you use a reducer but change camera maintaining the image scale through using smaller pixels...that won't make anything faster. 

[Rodd]

7 minutes ago, Adam J said:

A reducer should increase your per pixel photon collection rate though, that can be mathematically demonstrated. The problem comes when you use a reducer but change camera maintaining the image scale through using smaller pixels...that won't make anything faster. 

Yes--the overall FOV will increase in SNR a bit faster with a reducer--but this will not be 4x or 6x or whatever the difference between a 4" F5 and a 180mm F3.  The reason the hyperstar systems can yield such depth so quickly, and the reason the Epsilons can do the same is due to the combination of aperture and focal ratio.  Changing only one of those variables will not result in the blazing speed.  You need both.  So, use a reducer to increase FOV for framing reasons  ie large nebula, or to hide guiding issues if you have them.  Don't add a reducer thinking you will reduce your imaging time by 2-3x

Rodd

[Adam J]

49 minutes ago, Rodd said:

Yes--the overall FOV will increase in SNR a bit faster with a reducer--but this will not be 4x or 6x or whatever the difference between a 4" F5 and a 180mm F3.  The reason the hyperstar systems can yield such depth so quickly, and the reason the Epsilons can do the same is due to the combination of aperture and focal ratio.  Changing only one of those variables will not result in the blazing speed.  You need both.  So, use a reducer to increase FOV for framing reasons  ie large nebula, or to hide guiding issues if you have them.  Don't add a reducer thinking you will reduce your imaging time by 2-3x

Rodd

Well for a start its not 4x or 6x if you calculate it then you get (5/3)^2 = 2.8x faster, so your expectations are not inline with the mathematics. 

The second thing is that F-ratio = (Focal length / Apperture) so its litterally physically impossible to change only one of those variables since as soon as you change one you have by definition changed the other. 

Looking at reducers if you start out at a more typical F7 and reduce that via a 0.8x reducer to F5.6 that will give you (7/5.6)^2 = 1.56x faster not 2-3x faster as you seem to be expecting. 

Like I said above I think that your expectations for speed increase are not inline with what the mathematics predicts and hence you are naturally going to be disappointed. 

 

Adam  

[Rodd]

18 minutes ago, Adam J said:

Well for a start its not 4x or 6x if you calculate it then you get (5/3)^2 = 2.8x faster, so your expectations are not inline with the mathematics. 

The second thing is that F-ratio = (Focal length / Apperture) so its litterally physically impossible to change only one of those variables since as soon as you change one you have by definition changed the other. 

Looking at reducers if you start out at a more typical F7 and reduce that via a 0.8x reducer to F5.6 that will give you (7/5.6)^2 = 1.56x faster not 2-3x faster as you seem to be expecting. 

Like I said above I think that your expectations for speed increase are not inline with what the mathematics predicts and hence you are naturally going to be disappointed. 

 

Adam  

Its just not so.  First of all, I went from F5 to F3.  For each stop its 2x faster.  if your telling me its 1.8...no difference,  I just don't see it.  Not sure what you are talking about as far as focal ratio.  You certainly can change focal ratio independently of aperture and vice versa.   And you can change focal length independently of aperture.   When you use a reducer the aperture stays the same and you reduce focal length and focal ratio.  telescopes are not cameras.  The aperture is fixed,  focal length and focal ration change when a reducer is added.  My point is unless you change the aperture--there will not be a great increases in speed.  The proof is I still need 15-20 hours of integration regardless of whether I use a reducer or not.

And an Epsilon 180 IS 4x faster than an FSQ 106--no question--regardless of the FSQs focal ratio Why....BECAUSE OF THE APERTURE.

And I said dont add a reducer thinking you will reduce your imaging time 2-3x.  2.8x is 2-3x in my book. 

Rodd

Edited September 20, 2019 by Rodd