Baby leaves home...

[ollypenrice]

So it sounds like the FSQ85 is the one to go for if you want a trouble free imaging scope.

Yes, though Tom's 106N fluorite shows nothing like the shift seen in Maurice's animation, which I have seen before. My 106N doesn't move like that either but more testing is needed. It is certainly true that the 85 is the most painless faqt astrograph I've ever come across.

Olly

[latiniux]

Hi there!

I'm new to the forum and I got interested in this topic since I'm saving for a Refractor in order to use it with my full frame camera. I was thinking about the FSQ-85ED since I've read a number of positive reviews about it, but this post caught my attention regarding the image circle limit.

How is it that the Baby Q , as you call it, can't handle a 35mm chip? The Telescope specifications indicate a 44mm image circle.

Takahashi FSQ-85ED specifications
http://www.takahashi-europe.com/en/FSQ-85ED.specifications.php

When you say that the Atik's KAF-11002 needs a 45.24 mm image circle, where is that value coming from or how is it determined?

What about an SCT like the celestron's HD? All the models are supposed to have a linear image circle of 42mm and use large chips like a full frame dslr.

EdgeHD Optical Technology

http://www.celestron.com/university/astronomy/edgehd-optics

I guess what I'm trying to understand is how to chose a scope in order to use it along with a full-frame dslr or a kaf-11002 chip which is about the same size, based on the image circle specification so that I can chose correctly for the chip size.

Thanks a lot in advance for any light shed on this matter.

Regards

Agustin

[ollypenrice]

Hi there!

I'm new to the forum and I got interested in this topic since I'm saving for a Refractor in order to use it with my full frame camera. I was thinking about the FSQ-85ED since I've read a number of positive reviews about it, but this post caught my attention regarding the image circle limit.

How is it that the Baby Q , as you call it, can't handle a 35mm chip? The Telescope specifications indicate a 44mm image circle.

Takahashi FSQ-85ED specifications

http://www.takahashi-europe.com/en/FSQ-85ED.specifications.php

When you say that the Atik's KAF-11002 needs a 45.24 mm image circle, where is that value coming from or how is it determined?

What about an SCT like the celestron's HD? All the models are supposed to have a linear image circle of 42mm and use large chips like a full frame dslr.

EdgeHD Optical Technology

http://www.celestron.com/university/astronomy/edgehd-optics

I guess what I'm trying to understand is how to chose a scope in order to use it along with a full-frame dslr or a kaf-11002 chip which is about the same size, based on the image circle specification so that I can chose correctly for the chip size.

Thanks a lot in advance for any light shed on this matter.

Regards

Agustin

Hi Augustin,

It is actually quite hard to know the exact size of the 11 meg Kodak chip since I have seen some inconsistencies on the internet, but one figure that comes up is 37mm for the long side. I just used Pythagoras to determine the diagonal and thus the image circle needed. It exceeds 44mm.

In practice the Baby Q simply will not cover that chip. I am quite certain of this, having tried it. My friend Yves Van den Broek also tried it in his own Baby Q with SXVH36 CCD camera and he found the same edge distortions as I did. They were quite severe and certainly beyond anything you'd want to tolerate. I took this test shot to demonstrate a camera problem but it shows the distortion, particularly in the lower part. This is the largest version I have but if you zoom in on it then you'll see what I mean.

http://ollypenrice.smugmug.com/Other/Takahashi-EM200TEC140/i-8KDWWHh/0/O/test%20stackP1WEB.jpg

Of course, you DSLR chip may be a couple of mm shorter on the long side so the problem might be reduced or disappear altogether.

The Tak FSQ106 will easily cover current chips since it has an 88mm circle.

There are two problems with the Edge from your point of view. The large image circle only applies without the reducer so you'd be stuck with a painfully slow F ratio. On top of that the long focal length plays very badly with the small pixels of a DSLR.  If you use the reducer the image circle diminishes. I haven't used this scope so I can't comment from experience as I can with both Taks.

Cheers,

Olly

PS Finding scopes to cover full frame chips is not easy. I have used two others which do so. One is our TEC140 with official TEC flattener. That is a stunning scope to use. The other was made by a firm who have treated one of my own guests so badly (and are still doing so) that I will give them no publicity on here.

[kirkster501]

The FSQ85 is a lovely system!  I bought mine on Olly's recommendation and have not looked back  Following Olly's recommendations can get pricey, He also recommends the TEC140 ;-)

[ollypenrice]

The FSQ85 is a lovely system!  I bought mine on Olly's recommendation and have not looked back  Following Olly's recommendations can get pricey, He also recommends the TEC140 ;-)

Sorry mate! Not all my recommendations are expensive, though. I'm a great fan of the Fiat Panda, for instance. 

Olly

[Earl]

In all honesty I don't think it is really an expensive option, you can spend far more jumping from scope to scope trying to get one that really works, when you already knew what to buy in the first place.

I discovered this much to my cost and in some ways im still struggling with my 106 and automation due to not getting the right focus system in the first place.

[ollypenrice]

Yes, I know seveal people who've moved to the high end refractors via an assortment of scopes claiming to do the same job. Presumably they found that they didn't quite do the same job after all...

Olly

[Earl]

I have decided to take my own advice and get the 3.5inch Feather touch for my 106 with the official motorised controller on it, stop faffing and trying to patch the problem and solve it once and for all.

[ollypenrice]

I have decided to take my own advice and get the 3.5inch Feather touch for my 106 with the official motorised controller on it, stop faffing and trying to patch the problem and solve it once and for all.

I'm surprized by this. What's wrong with the 106 focuser?

Olly

[Earl]

Nothing is wrong with it Olly, its down to motorising it, and that is where the issue is.

There is no backfocus to put a FLI Atlas  with the scope reduced unless you completely remove the existing focuser and get special adapters made by Precise Parts, and we talking big money. by the time its on your doorsetp.(2.5K+?)

I want a motorised option specifically designed to fit the focuser in a non DIY style,

Focus is critical especiall at F3.6 with a scope that is not the most friendly with thermal shft , i dont need to teach you to suck eggs there LOL, and It has to be fully automated for me and be 100% reliable.

This is the weak part of my setup and needs to be nailed.

Edit: I have been chasing my tail, with lakeside / robo focus etc and im sick of continuing issues, none of these are issues with the said equipment, but issues it getting it to do what it should reliably and repeatable, I dont have the manual dexterity to fine tune beyond a point and its beyond that point i need to resolve.

[Martin-Devon]

I'll be interested to see how you get on with the upgraded motorised focuser Earl and whether this really does address the issues that you are having. I have a Lakeside fitted to my stock FSQ106 focuser and it works a treat (with Focusmax4), no issues at all - the only pain and it's a real one, is having to refocus every 20 minutes or so due to the inherent thermal & contraction properties of the FSQ106, which are a "feature" of the scope I am told. 

Martin

[Earl]

I'll be interested to see how you get on with the upgraded motorised focuser Earl and whether this really does address the issues that you are having. I have a Lakeside fitted to my stock FSQ106 focuser and it works a treat (with Focusmax4), no issues at all - the only pain and it's a real one, is having to refocus every 20 minutes or so due to the inherent thermal & contraction properties of the FSQ106, which are a "feature" of the scope I am told. 

Martin

Agreed and it should work as intended, but im just not finding this the case so im taking a sledge hammer to crack the walnut LOL

I played with it last night in the house, and had the scope vertical with the focuser doing push-ups with a fully loaded ccd etc, and outward was fine, but inwards i can see the opposite focus knobs not showing fine movement all the time, there is the odd little jump here and there this is a good example of the problems im having.

It was doing 7000 steps out and 7000 in, where before my tinkering 7000 out but a random amount back in upto 12000...

[ollypenrice]

Anyone reading this thread might see the attraction of a second hand fluorite FSQ106N, perhaps. You don't get the opportunity to use the reducer but the focus drift we experience is nothing like as bad as this. It's fairly typical of any fast refractor, in fact.

On his TEC I know that Per used a 3D printer to make a bracket which lets the motor drive the main shaft of the focuser directly. I fitted it to the scope myself since it's living in our robotic shed and it works a treat.

Olly

[Earl]

Th N was something I did ponder on, but I decided i liked F3.6 and had to tackle the focus automation as preferance.

[paulastro]

I sympathise with your feelings on selling your scope Olly. I've sold scopes myself that have served me well for pragmatic reasons. It's like saying goodbye to an old and faithful friend. At least you have a worthy replacement.

I loved the image by the way. Regards, Paul