TAK FSQ 106 at F3b or OS RH 200 at F3

[Rodd]

I am torn between the FSQ 106 and .6x reducxer at F3 and the OS RH200 at F3.  I love refractors for their quality and simplicity, but I like the idea of 8" of aperture.  Slightly different focal length--I am mostyly looking at speed as I am tired of having to collect 20 hours of data over a months time due to the weather.  Which scope would be faster?  Which would produce better images?  Any thoughts?

 

Rodd

[Rodd]

Really--no one has an opinion?

Rodd

[andrew s]

A would go for the larger aperture. More photon means better S/N with the image processed at the same image scale etc.

Regards Andrew

[Rodd]

 

On 8/12/2017 at 12:09, andrew s said:

A would go for the larger aperture. More photon means better S/N with the image processed at the same image scale etc.

Regards Andrew

There is so much more to it than that.  One must calculate the time lost to tilt issues, collimation issues.  One has a Focal length of 600 the other 318 at this focal ratio-so comparing is difficult.  The 106 is proven and very good.  The OS is superlative on paper.  Anybody put it to the test?

Rodd

[andrew s]

12 hours ago, Rodd said:

There is so much more to it than that.  One must calculate the time lost to tilt issues, collimation issues.  One has a Focal length of 600 the other 318 at this focal ratio-so comparing is difficult.  The 106 is proven and very good.  

Then I propose you do the sums yourself rather than ask for input and turn your nose up when an opinion when it is given.

Regards Andrew

[Rodd]

2 minutes ago, andrew s said:

Then I propose you do the sums yourself rather than ask for input and turn your nose up when an opinion when it is given.

Regards Andrew

Easy, Gov'ner

[Ant]

Sorry, I'm with Andrew on this one! 

[Rodd]

4 minutes ago, Ant said:

Sorry, I'm with Andrew on this one! 

With respect to his choice, or his ire?

Rodd

[Ant]

His ire.

[Rodd]

12 minutes ago, Ant said:

His ire.

Its called a discussion, gentleman--that's what forums are for.  

Rodd

[pete_l]

15 hours ago, Rodd said:

 

There is so much more to it than that.  One must calculate the time lost to tilt issues, collimation issues.  One has a Focal length of 600 the other 318 at this focal ratio-so comparing is difficult.  The 106 is proven and very good.  The OS is superlative on paper.  Anybody put it to the test?

Rodd

Well, you asked 2 questions:

Which would be faster? And the answer is that since they are both more-or-less F/3 it is a tie.

Which would produce better images? Personally I would go with the larger aperture, since there is very little in the sky that would need a 318mm focal length FoV and $7k is a lot to spend just to fill your frame with stars! In each case your image would build brightness at the same rate ((both being F/3) but the 600mm FL would make your actual target larger in the frame.

[Rodd]

27 minutes ago, pete_l said:

Well, you asked 2 questions:

Which would be faster? And the answer is that since they are both more-or-less F/3 it is a tie.

Which would produce better images? Personally I would go with the larger aperture, since there is very little in the sky that would need a 318mm focal length FOV and $7k is a lot to spend just to fill your frame with stars! In each case your image would build brightness at the same rate ((both being F/3) but the 600mm FL would make your actual target larger in the frame.

If that is the case-- I do not mind a large FOV for Widefield (I already have mid and long focal lengths covered)--especially if I get the ASI 1600mmcool with its little pixels--the scale would be 2.39 arcex per pixel which is pretty good for wide field.  But, here is the real question--I know they are both F3, but for a certain focal length, aperture will effect speed.  An 8" scope with a 500mm FL at F3 will be faster than a 4" scope with a 500mmFL at F3.    But the focal lengths are not the same here.  As I am out for speed, I am trying to determine which scope would be faster.  And--would there be a significant difference.  In other words--would the extra 4-5 inches of aperture make up for the 2x focal length as far as speed.  And its not single sub speed I am most concerned with--its whole image speed.  I want to complete an image in 4-5 hours total exposure time.  

The other interesting point is the 106 is many, many times more commonly used than the OS scope.  I am wondering why.  For me,needing  ASI1600mmcool camera, OAG, guide scope and USB port if I get teh 106, the cost of the 2 systems would be comparable (within $500), so teh $ is removed from teh equation.  My choices for speed were

1) Epsilon 180

2) FSQ 106 at F3

3) OS RH 200 at F3

(not interested in Hyperstar or RASA)

Rodd

[Rodd]

Here is another--far cheaper option.  Use the Televue np101is at F4.2 (reduced) and get the ZWO ASI 1600mmcool camera.  Will the sensitivity of the ASI 1600 coupled with the F4.2 speed of the Televue, be faster than my current STT-8300 and the Televue.  If the answer is yes, this may be a good option.  Ther np101is is a fine scope and I have always wanted an ASI 1600mmcool.  

Rodd

[ollypenrice]

3 hours ago, pete_l said:

Well, you asked 2 questions:

Which would be faster? And the answer is that since they are both more-or-less F/3 it is a tie.

Which would produce better images? Personally I would go with the larger aperture, since there is very little in the sky that would need a 318mm focal length FoV and $7k is a lot to spend just to fill your frame with stars! In each case your image would build brightness at the same rate ((both being F/3) but the 600mm FL would make your actual target larger in the frame.

There's very little in the sky that would need a 318mm focal length? Can't agree with that! The original and exciting new structures are likely to be the very large scale ones. There are vast nebulae, gloriously beautiful, which tend to need the mosaic approach. An initial widefield is a great starting point.

(Focal ratio: F3 is always the same as F3? It certainly isn't; oh no, not the F ratio myth again! Why does my neighbour/colleague's F8 Ritchey Chrétien saturate his chip in a couple of minutes? Because it has 0.8 metres of aperture!)

There are fantastic ultra widefield images to be made within the Milky Way and, if you want the full wide field, a fast F ratio is indeed useful. Ironically, though, we find here that we want to do mosaics using our widefield setup while our longer FL one does single panes, mostly. So the wider your field the more tempting are the mosaics - because there are so many truly vast structures out there.

Olly

 

[Rodd]

33 minutes ago, ollypenrice said:

There's very little in the sky that would need a 318mm focal length? Can't agree with that! The original and exciting new structures are likely to be the very large scale ones. There are vast nebulae, gloriously beautiful, which tend to need the mosaic approach. An initial widefield is a great starting point.

(Focal ratio: F3 is always the same as F3? It certainly isn't; oh no, not the F ratio myth again! Why does my neighbour/colleague's F8 Ritchey Chrétien saturate his chip in a couple of minutes? Because it has 0.8 metres of aperture!)

There are fantastic ultra widefield images to be made within the Milky Way and, if you want the full wide field, a fast F ratio is indeed useful. Ironically, though, we find here that we want to do mosaics using our widefield setup while our longer FL one does single panes, mostly. So the wider your field the more tempting are the mosaics - because there are so many truly vast structures out there.

Olly

 

Yes...and a plus would be that even though a mosaic is the plan, each of the panels would make a pretty good image in itself.  However, bear in mind that even if I get the FSQ 106 and shoot at F3 with either my STT-8300 or the ASI 1600mmcool--it isn't really a widefield setup.  Not like a KAF 11000, 16803, or ATIK 16200, to name a few.  That is one reason this decision is so difficult, because its not only what I will be able to do now, but what is possible with future additions/modifications without redundancy (or limiting redundancy)  

The real question is--which scope would more likely allow me to complete an image in 1 night--whatever type of image it may be--whether a widefiled image, or a narrow filed image.  I will take the image for what it is--so no myth involved.   I can use either camera on either scope.  the primary variable that I want to target is speed.  What ever I can get in a short amount of time.  If I set up a true widefiled kit, I will want to set that up so as not to be constrained by anything but image quality (which will include speed I am sure, but it won't necessarily be the driving factor).  Unfortunately cost is always a factor.  At present I see 3 choices.  Buy the ASIO 1600 and use it with the Telvue at F4.2 (pixel scale of 1.81), Or get either the FSQ or OS RH200 and use them with the STT-8300.  I can't buy them all!

Rodd

[andrew s]

1 hour ago, Rodd said:

The real question is--which scope would more likely allow me to complete an image in 1 night--whatever type of image it may be--whether a widefiled image, or a narrow filed image.

If that is really what you want to do get the largest aperture telescope you can afford with a front illuminated CCD with 90% + QE. 

Regards Andrew 

[Rodd]

Just now, andrew s said:

If that is really what you want to do get the largest aperture telescope you can afford with a front illuminated CCD with 90% + QE. 

Regards Andrew 

How does front or back illumination effect speed?  The highest QE I know of is %76-80, can't recall the camera--it may very well be the ASI 1600--or one of the HAD chips.   That is what makes this particular choice very difficult--the cost is about the same for me (due to what I need to get to set it up the way I want).  Also--I have to be able to use my current mount (Mach 1)--so I am limited to a fast Newt of about 8" (maybe 10 for some brands).  But they are F4.  Plus I don't like diff spikes and avoiding collimation issues would be easier with a higher end scope.  Maybe an ASA.   Anyway--there is paper and theory, and then there is reality-not always the same.  For example binning 2x2 is suppose to be 4x faster than 1x1.  It is not.  Not even close.  so some personal experience would be great--even anecdotal.    I know Paddy uses an OS RH 200.

Rodd

[andrew s]

Google E2V back illuminated CCDs. By being back illuminated the light does not have to travel through the gate structure and thus have higher QE. Here is an example http://www.flicamera.com/microline/index.html  go to the back illuminated tab.

26 minutes ago, Rodd said:

Plus I don't like diff spikes

Then that rules out the 

 

5 hours ago, Rodd said:

Epsilon 180

and 

5 hours ago, Rodd said:

 OS RH 200 at F3

so you are left with the

5 hours ago, Rodd said:

FSQ 106 at F3

or your 

 

4 hours ago, Rodd said:

Televue np101is at F4.2 (reduced)

Regards Andrew

[Rodd]

5 minutes ago, andrew s said:

Google E2V back illuminated CCDs. By being back illuminated the light does not have to travel through the gate structure and thus have higher QE. Here is an example http://www.flicamera.com/microline/index.html  go to the back illuminated tab.

Then that rules out the 

 

and 

so you are left with the

or your 

 

Regards Andrew

The OS RH200 does not have diff spikes I do not believe.  The FLI cameras are big bucks (I would need a big sensor with small pixels--quite rare). 

[andrew s]

10 hours ago, Rodd said:

The OS RH200 does not have diff spikes

Correct I ws mistaken  it has a full aperture corrector. 

 

12 hours ago, Rodd said:

The real question is--which scope would more likely allow me to complete an image in 1 night--whatever type of image it may be--whether a widefiled image, or a narrow filed image.

If this is still your goal then aperture is king. Why did you rule out the Rowe Ackermann Schmidt astrograph at 11" of F2.2 and a modern OSC camera it would do as you ask. Although the light pollution filter would be a must in most loctions.

Regards Andrew

PS Look at the images in this review https://astronomynow.com/2016/06/01/celestron-rowe-ackermann-schmidt-astrograph/

and here https://www.astrobin.com/gear/48166/celestron-rowe-ackermann-schmidt-astrograph/

[Rodd]

3 hours ago, andrew s said:

Correct I ws mistaken  it has a full aperture corrector. 

 

If this is still your goal then aperture is king. Why did you rule out the Rowe Ackermann Schmidt astrograph at 11" of F2.2 and a modern OSC camera it would do as you ask. Although the light pollution filter would be a must in most loctions.

Regards Andrew

PS Look at the images in this review https://astronomynow.com/2016/06/01/celestron-rowe-ackermann-schmidt-astrograph/

and here https://www.astrobin.com/gear/48166/celestron-rowe-ackermann-schmidt-astrograph/

Regarding the Rowe--I have never been a fan of the front mounted camera--The cable issues, diff spikes, plus it weighs a bit much for my mount (I can image with 45 and the OTA alone it weighs 36.  I would definitely go for the RASA over hyperstar though-

Regarding the aperture issue, here are my concerns

1) The OS RH 200 is not a full 8 inches due to the 30% obstruction, so it actually is slower than F3, while the FSQ 106 is a bit more than 4" and it would shoot at F3

2) The OS scope carries tilt and collimation frustration, which equates to loss of imaging time. Maybe its not as bad as "they" say--but it certainly is worse than the FSQ

3) There is also some evidence that there can be star bloating in the OS RH 200 but I do not know the details.

4) The FSQ has 2 ED lenses, is fully corrected, has a monster imaging circle, and is proven.  I like the TOA 130 stock focuser (never tough it manually  or with eyepiece so I don't know what all the fuss is about)-so I won't have a problem with the focuser of the FSQ--while I may need to concern myself with the focuser of the OS RH 200--not sure.  

The FSQ 106 is one of the most popular imaging scopes out there.  It is tauted as being among the best refracting astrographs available (possible only exceeded by the FSQ 130--Hmmmm---maybe that would be better).  Yet you would not suspect this to be the case from the comments on this thread.   From this discussion, one could conclude that both scopes are wild cards, and aperture is the deciding factor.  Maybe it is...I don't know.  But then why are not more people using them?  I don't know.  

I am n ot saying you are wrong in "aperture IS the deciding factor".  I shoot with 11" at F7 and quite frankly I don't see any difference between the C11Edge at F7 and the TOA 130 at F7.7 as far as speed goes.  Maybe a little, hard to say--and teh difference in aperture there is 7 inches.   

 

[andrew s]

Looking at your kit list you already have a wide range of options so not sure if you know what your seeking other than a new toy. (I get like that too.)

Between the OS RH200 and the FSQ 106 toss a coin. Don't go on the toss but your emotional reaction to it. If it come up FSQ and you feel good get it if you feel disappointed get the OS RH200.

I am sure you can make either sing.

Regards Andrew

 

[Rodd]

3 minutes ago, andrew s said:

Looking at your kit list you already have a wide range of options so not sure if you know what your seeking other than a new toy. (I get like that too.)

Between the OS RH200 and the FSQ 106 toss a coin. Don't go on the toss but your emotional reaction to it. If it come up FSQ and you feel good get it if you feel disappointed get the OS RH200.

I am sure you can make either sing.

Regards Andrew

 

The option I don't have is SPEED--Even with the TVnp101is at F4.3 I shoot 20 hour images.  That equates to weeks of time due to inclement weather/Moon.  Focal reducers are great at widening the FOV--but time reduction is not as clear cut (the myth).  That is the biggest reason I do not get the FSQ--it will be reduced to F3.  I don't see much difference in time between the TV at F5.4 and F4.3.  I am not confident that the FSQ will be as fast as the OS because of this.  But thank you for your input--I am thinking about things from a slightly different angle now, which is gppd

Rodd

[ollypenrice]

15 minutes ago, Rodd said:

The option I don't have is SPEED--Even with the TVnp101is at F4.3 I shoot 20 hour images.  That equates to weeks of time due to inclement weather/Moon.  Focal reducers are great at widening the FOV--but time reduction is not as clear cut (the myth).  That is the biggest reason I do not get the FSQ--it will be reduced to F3.  I don't see much difference in time between the TV at F5.4 and F4.3.  I am not confident that the FSQ will be as fast as the OS because of this.  But thank you for your input--I am thinking about things from a slightly different angle now, which is gppd

Rodd

The deadly myth only applies to objects which fill the frame without reducer. If you want the whole frame then the fast F ratio really is faster.

You take 20 hour images because you want very good images and you succeed in making them.

Nothing will take the risk out of a very fast system. Even the FSQ does not have a perfectly clean copybook. There are plenty of reports of tilt issues from the reducer and its three mysterious grubscrews on the subject of which Japan is silent as the grave.

I remain convinced that the only risk free route to very fast imaging is the dual (or multiple) rig. Two Star 71s side by side?

The presence of 'risk' in fast systems does not indicate that they will never work, let it be stressed.

Olly

[Rodd]

7 minutes ago, ollypenrice said:

The deadly myth only applies to objects which fill the frame without reducer. If you want the whole frame then the fast F ratio really is faster.

You take 20 hour images because you want very good images and you succeed in making them.

Nothing will take the risk out of a very fast system. Even the FSQ does not have a perfectly clean copybook. There are plenty of reports of tilt issues from the reducer and its three mysterious grubscrews on the subject of which Japan is silent as the grave.

I remain convinced that the only risk free route to very fast imaging is the dual (or multiple) rig. Two Star 71s side by side?

The presence of 'risk' in fast systems does not indicate that they will never work, let it be stressed.

Olly

That sharpens the focus!  If I am going the dual rig route--why not use the np101is I already have and get.....yet another np101is (talk about redundancy).  I suppose the 2 scopes don't have to be identical.  An FSQ at F5 would work with the TV at F5.4 I suppose.  But.....I think that the word "Risk" must be used with respect to mounting concerns, dual computer use, dual camera use, etc. 

And here is a statement some one said regarding the np101is (or any fast refractor) and the OS RH200 ....."there are faint details descernable with the OS scope that will NEVER be reachable with the np101is regardless of the length of the exposures".  This is similar to the many short exposures vs 1 long exposure.  There are photons captured at 30 min that give detail that just can't be had with 60 sec exposures, regardless of the number of 60 sec exposures--even a million. They are so faint that it takes 30 min for the signal to reach a level of detection.  So my question is if you use 20 F10 scopes and I use 2 F5 scopes and we both take 1 min exposures, would the images be similar?  

The dual rig sounds great--I do have mounting concerns and weight concerns--not to mention logistics concerns.  But maybe I will think about it.

Rodd