TAK FSQ 106 at F3b or OS RH 200 at F3

[ollypenrice]

2 minutes ago, Rodd said:

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

If someone said that the RH could catch details not available in smaller apertures because the Dawes Limit is proptional to aperture then I'd accept that they had a point.

And if we imaged from space they'd have a point about the photon density advantage of the RH as well. (And if we had cameras of enormous dynamic range so we didn't have to worry about the high end of the brightness range saturating.) But since the faintest detail is consumed by the sky fog (even where I live) I'm not persuaded by the argument. The RH has no more power than any other optic to subdue ambient sky brightness without subduing faint signal. It will find more stars, though. (Advantage? Disadvantage...?)

Olly

[Rodd]

I was more referring to the long exposure vs many short exposure issue--maybe the 2 issues (scope type and exposure length should not be mixed).  With a given scope, no amount of 20 sec exposures can reveal the faint details reachable with a 1 hour exposure--or lets say with the maximum exposure for a given location with respect to sky fog).  True?

[ollypenrice]

51 minutes ago, Rodd said:

I was more referring to the long exposure vs many short exposure issue--maybe the 2 issues (scope type and exposure length should not be mixed).  With a given scope, no amount of 20 sec exposures can reveal the faint details reachable with a 1 hour exposure--or lets say with the maximum exposure for a given location with respect to sky fog).  True?

Certainly true in the case of CCD. Low read noise CMOS are changing the rules, though.

Olly

[Rodd]

14 minutes ago, ollypenrice said:

Certainly true in the case of CCD. Low read noise CMOS are changing the rules, though.

Olly

Enter the ASI 1600.  the camera is begging to be used it seems.  But shorter total exposure time is not what it represents, which is what I want.  I am not really interested in many short exposures vs fewer longer exposures with similar total integration time.  Due to the bit depth, you have to stack 200-300 (per filter) to compensate.  Not familiar with other cameras.

Rodd

[ollypenrice]

3 hours ago, Rodd said:

Enter the ASI 1600.  the camera is begging to be used it seems.  But shorter total exposure time is not what it represents, which is what I want.  I am not really interested in many short exposures vs fewer longer exposures with similar total integration time.  Due to the bit depth, you have to stack 200-300 (per filter) to compensate.  Not familiar with other cameras.

Rodd

No free lunch...

[Rodd]

Free is certainly not a description I would use in this pursuit!  But now you have me thinking.  As a person who knows nothing about running a duel system, it seems to me that running 2 independent systems is simpler.  I just do what I do now on 2 units.  Since I need to buy a major piece no matter what path I choose, I have  more options.  Which of these makes more sense:

1) Purchase new mount (AP1100-capacity 110 pounds) and use it for a duel setup of TOA 130 at F5.4 (reduced) FL of 700mm, and the Televue np101is, FL 5.4 (unreduced) FL of 540mm.  This option also allows me to use 2 independent systems if I just can't get the duel setup working.  Also, it sets me up for adding a bigger OTA at some point.  If I calculate it right I would be shooting at an effective focal ratio of 2.7.

2) Purchase second np101is or FSQ and try to run duel setup on my current mount.  Assume the weight works (it will be close, but I think its dooable).  This option allows for the use of the FSQ singly with .6x reducer fopr F3

3) Buy the OS RH200 and use it by itself on my current mount.

Rodd

[ollypenrice]

My own setup tells you what I would do...

Olly

[Rodd]

2 minutes ago, ollypenrice said:

My own setup tells you what I would do...

Olly

Not really--you would either do 1 or 2--but which

[ollypenrice]

9 minutes ago, Rodd said:

Not really--you would either do 1 or 2--but which

Well I'd start with the mount I had. Weight is only half the story. What really matters is remaining with a guiding RMS of about half the pixel scale of the imaging cameras. If you get that it ain't broke and won't need fixing.

Olly

[Rodd]

I have to pick a lane and keep at it--no changing lanes after a purchase like this! When not overloaded I get rms errors  between 0.05 and 0.25 arcsec (usually below .2 more than this and I tinker).  How else to know but by weight?   All I can do is calculate the reported weights of the various items and see if it is below the stated capacity of the mount.   I recalculated the FSQ with a 3 pound camera and np101is with a 6 pound camera--I think its too much weight for the Mach 1-certainly right at the limit.  I would need to get a second np101is (5 pounds lighter).   But getting a second np101is is the least appealing purchase in front of me.

Rodd