is there a handy link that shows separation calendar/time?
|
|
|
Nice challenge!
I may take you up on it.
Stan
|
Has anyone imaged Charon? Not a full fledged dbl split. But enough of a bump or elongation, in the right place, to say you got it?
If you've ever seen the discovery photo of Charon, taken with the Naval Observatory scope S of Flagstaff, you realize how little of a bump on an otherwise round "star" it is.
I thought I'd try for it this summer. My 14" scope and camera, with it's FL and pixel size, indicated it might be? possible. Unfortunately the seeing on the handful of possible nights never gave me a chance, except for possibly one night. I haven't done the refinement of the subs to tell for certain yes or no, but hot off the press was not encouraging.
I see Stellurium will give you the position of Charon at any given time. So at least you know where it aught to be.
Years ago when I asked this question, I was told to forget about it. Not even close to maybe. But equipment and techniques have improved A LOT, And I'd bet someone has done it, or could. Maybe it's even a common check marker among master and high end journeymen imagers?
One of these days, just to add it to my "planets" collection, I'd like to get Eris. At mag 18.7 it should be no problem. Humana and MakeMake even though brighter, just don't have the same cache, for me. Sedna at 21.1 might be beyond reach.
|
Re: C11 Edge is not suitable for guide scope tracking
"...perfectly adequate new OAGs for $150-$250"
Yes, we are lucky to have the variety and competition we do these days.
I did initially get and try an adequate $250 OAG. But, but, but, but, but....
And so, since SBIG (Diffraction Limited) was offering $1000 off on a camera, FW with integrated guider (with? f7 reducer), and RGBL & narrow band filters pkg, well there went $2k,
And as long as I was at it, a rotator, a secondary focuser, and AO and now I'm somewhere around 5k. Ridiculous. But it is a choice. And got me where I was heading eventuially anyway. And it all fits exactly in to Celestron's back focus spec. Exactly.
Unfortunately the Pyxis rotator creates some vignette problems, often forcing rotation to find an adequately bright star. I would not recommend it. I've taken it out and replaced it with a spacer, and now for example the faint and few stars N of the Deer Lick group have become plenty bright and adequate for guiding.
I highly recommend the absolute position secondary Optec focuser. Great instrument. Better imo than any other motorized focuser. Now that I have locked down the main mirror, in all directions, I don't have to move it again, including changing btwn f7 to f10
I was originally disappointed with the AO.because not often is there a bright enough star to take advantage of it's AO speed. I do find though that it eliminates mount backlash problems, and helps with most other mount issues.
|
Hey Stan.
First, nice work with the emccd. I see you said in a previous post that your ecposure was .125x56k. Are you saying you stacked 56thousand frames? If so, what rack of blade severs are you using or was IBM's Watson involved? :)
Can you give a link to a second hand laboratory liquidators website?
Dave
|
Re: C11 Edge is not suitable for guide scope tracking
AO is a plus on these scopes.
Stan, are you still down at RH? Are your hd11 tests with EMC from RH/super datk site with very good seeing?
Dave
PW14/AP305RH
DSW
|
Re: C11 Edge is not suitable for guide scope tracking
" several thousand?for a good OAG system"
Google "Off axis guider for SCT" and you'll find perfectly adequate new OAGs for $150-$250 from OPT, Lumicon, Celestron, etc.. ?Used ones come up somewhat regularly on Astromart for about $100.
Overpriced OAG are motorized (entirely unnecessary) or have fine-focusing (also unnecessary) ?and often integrated with CFW / AO (AO is definitely worthwhile). ?They are heavy and unwieldy. ?There is no need to go overboard.
Meade are definitely heavier but that's one reason I prefer Celestron. <g>
Stan
|
Re: C11 Edge is not suitable for guide scope tracking
"?what was wrong with the mirror locks?"
Hi Dave
Imo, nothing.?The mirror locks work very well holding and maintaining?the mirror "flat" relative the rest of the optical components,?even?though?the mirror?shifts sideways. When I stopped the mirror shifting laterally, the star trail?problems stopped too.
Fwiw, and imo related, The doughnut hole of?a defocussed star, when looking at a star at the zenith vrs near the horizon, shifts a little, but not a much. However?a?dust particle, (becoming nicely visible?in the defocused state)??shifts A LOT, In fact about as much as a star would trail over that same amount of OTA?movement.
As for differential flexure of?the many of the components,... with an?identical setup put?on either?the?C11 or Meade 10" OTA, swapping only the OTA,?the problem would?come or?go, respectively, to the same amount, every time.
I did?wonder if the C11 OTA was flexing?so much?as to be?part, or all,?of the problem.?The Meade castings (classic, circa 1997)?are heavier, and?the connecting tube is both?glued and bolted to both?the front and rear castings. The C11 castings are lighter, and?are?bolted only. But once I?prevented the mirror from shifting? relative to the rear casting, that?pretty much solved the problem, so?I'd have to say flexure of the OT?is not much of a problem. I'd bet the built in mounting rail is?a necessary part of the?structural rigidity. I have one on top too, which probably helps too.
I don't mind going to OAG. It's just that I was forced to well?before I was ready to.?Along with the C11 Edge, I bought a cooled CCD camera to replace my DSLR. That meant I would be able to?go beyond the?10-15min?subs I was accustomed to getting.?Given the info Celestron provides about the Edge, I think it was?reasonable to?expect I'd be able play with my new camera and scope for a year or so, using a guide scope,?within the 10, maybe even 15min?limits,?before spending the $?for OAG, to go further.
|
Re: C11 Edge is not suitable for guide scope tracking
Hi Stan,
Yes I am aware of the issues,?both of?mirror shift, differential flexure, and others?too. I?learned much about, and?successfully dealt with those issues?with my 10" Meade classic?and its?piggyback?guide scope. I regularly?got good 10min exposures with that combo. 15min exposures averaged?~70% acceptable.
The last paragraph on p13 of the Celestron Edge?white paper?is simply wrong Where they recommend?their 80mm piggyback?guide scope for?sub-exposures up to 10 min.?But? they also state you?may want?to "consider" an OAG if?"...exceeding 10min or so."
Apparently Celestron's warrantee dept doesn't know the C11 Edge can?in no way?meet this expectation.?They?sent me?2 replacement?scopes, expecting I guess that one of them would perform as described. They can't. I guess it's possible I got a batch of?3 new?scopes, over a 9 month period,?all equally?"bad".
Actually, outside of this particular?bone of contention, I have no other complaint. The stars are tight and bright across?a KAF 8300 chip, and?quite good to the OA chip too. That is what I expected. I just wasn't expecting to? Have to?spend, at least not right away,?another several thousand?for a good OAG system too, because it IS?necessary?over 100 sec or so, no matter what they?print otherwise.
Given my experience, I'd have to say that given?the?many?issues?with guide scopes and mounts, they?are used as reasons why a user can never seem to?get good results with a guide scope, when to begin with there is a show stopper issue with movement of their main mirror.
BTW Stan, I've been following your comments and experiences with short expose and accumulate subs?using CMOS chips. Thanks for pioneering. It certainly seems their?might be?a future?there.
Regards,
Ettu
|
Re: Installation of a FeatherTouch SC Microfocuser. Hard to turn focuser knob..fix?
Talked to StarLight instruments.? The brass stop tolerance vs the Celestron focuser shaft tolerances have recently been an issue and have resulted in difficulty with turning the focuser.
Will be a warranty repair.?
|
Re: Installation of a FeatherTouch SC Microfocuser. Hard to turn focuser knob..fix?
This will be hard to describe but I will try.? Ultimately I found one issue that made the turning of the focuser difficult.? I found that there is an issue with the threads of the brass stop (as described in the installation sheet).? It seems that the brass stop binds and becomes difficult to turn, when the focuser shaft reaches the end of the threads in the brass stop.? I visually inspected the threads under magnification, and found no issues such as burs or cross threading marks.? I threaded the brass stop in the opposite direction and found that issue is with the end threads on the focuser side of the brass stop. ? I used some steal wool to smooth the threads and then polished the threads.? The focuser was then re-assembled and the focusing is definitely improved.? The force needed to turn the focuser increases as the scope turns towards zenith though.?
A second issue ... the fine focus seems to fail when the force increases past a certain point.? This renders the quicklync motor focuser useless.? This seems to be a "broken" part problem.
I now have concluded that I just need to keep the focuser base screwed to snug and no more.? The alignment arbitrarily takes care of itself.
I have found that everything else is good.? The mirror glides smoothly and evenly, in and out.
I don't know if these problems are a result of initial problems of installation or if they came with the product from the manufacture.? I put in a message to starinstruments but Wayne is out of the office for a week ...uggg.
|
" What camera are you using?"
It is an esoteric 2nd hand EMCCD. ?Such cameras are primarily made for microscopy and typically cost near $20k but used ones infrequently appear from laboratory liquidators at vastly discounted prices. ?I had to write the camera control, acquisition and processing software (microscopy software is inappropriate and ridiculously expensive).
"Are you using a reducer?"
Never!! <g>
All are prime focus. I regret not using a Barlow for M13 because that was a very good night and the image is seriously undersampled at 0.6"/pix (fwhm = 1.6" for that pic).
Stan
|
Stan, ? What camera are you using? Are you using a reducer? ?
toggle quoted message
Show quoted text
From: C14_EdgeHD@... [mailto:C14_EdgeHD@...] Sent: Thursday, August 3, 2017 12:08 PM To: C14_EdgeHD@... Subject: [C14_EdgeHD] Edge C11 1st lights ? ?
|
|
|
Re: C11 Edge is not suitable for guide scope tracking
" The main mirror is shifting within the OT"
You have affirmed what legions of SCT imagers have known for decades. ?I'm surprised that you were unaware of this, as it is often discussed in many forums.?
There are marginal cures, such a "Flop Stoppers". But piggy-back is inherently problematic - the primary is not the only component subject to flexure and solving it may not actually solve the real problem. ?
OAG is the standard "best" solution but can be a real pain. ?A high quality and precisely aligned mount goes a very long way. ?
And the low read-noise of newer cameras permit shorter exps that can eliminate the need for any type of guiding (other than keeping the target within the frame). ?CMOS is still problematic for most DS but the very low noise promises sub-exps as short as 5-20 sec that do not benefit from guiding. ?
This is an extreme example, but here is a recent image made with my new Egde C11 using EMCCD at 8fps (0.125 sec x 55k frames) with no guiding:
Stan
|
Re: Installation of a FeatherTouch SC Microfocuser. Hard to turn focuser knob..fix?
Not to say it doesn't happens but I've never seen this non-orthogonal issue and I've installed several Feather Touches and have friends who've done likewise. ?If I were to identify such a problem I would be inclined to investigate why (i.e. a defect in the mirror mount?) but if it can be "fixed" by tilting the FT then that is probably adequate.
Your description of the "tight nut" seems to imply that the problem is solely within the FT unit? ?They are expensive so I would not mess with it and return it as a defective unit. ?But if that issue is within the SCT itself it is not so easy to return and the warranty may have expired, in which case you are on your own.
BTW, every FT I've used is silky smooth.
Stan
|
Re: C11 Edge is not suitable for guide scope tracking
you can get mirror flop with oag. using a guide scope your error is more than likely differentiy flexure between the two systems.
what was wrong with the mirror locks?
I know people on cn shooting hour long subs with an hd11 and oag.
most serious imagers are using oag on most telescope designs now a days.
Dave
|
Re: Installation of a FeatherTouch SC Microfocuser. Hard to turn focuser knob..fix?
When you attach the focuser just pull the mirror back and forth. It should slide very smoothly. If you cannot pull the mirror through its entire range and do so very smoothly, you have other issues.
When you have the focuser in hand and turn it, it should be very smooth. If both of these tests work then it is your alignment of the focuser. Perhaps your observations have turned up another flaw but the alignment is critical.
Gary
Carpe Noctem
Sent From My LG-V10 Phone
On Wed, Aug 2, 2017 at 4:10 PM -0700, "gdunham@... [C14_EdgeHD]" <C14_EdgeHD@...> wrote:
?
Worked with the focuser this afternoon.? I isolated a single problem.? The brass nut that turns on the mirror focus rod was binding at the outer edge of the thread.? Visual inspection under magnification shows not burs or cross threading.? It may be that it is engineered to have a tight end. ? I would like to put it on a tap but in the mean time I smoothed and polished the threads.? I put it back together and found that it turns a bit easier.? My final step of screwing in the 3 screws.? I did find that no matter how I tightened them, the focuser became bound.? I ended up tightening just to take out "slack".? Seems OK.? I am anticipating that there may be problems when the mirror is at a bottom position.? I will not really know if the problem is solved until I have a star to focus on.?
Thanks for the heads up on the mounting plate screw issue...it is a very sensitive and requires great care to get right.? I am not sure it should be like this and plan on contacting StarLight instruments and talk about my installation.
|
Re: C11 Edge is not suitable for guide scope tracking
Today I have a follow up to my original note declaring that the C11 Edge, at f7 or f10,?is not suitable for guide scope tracking for anything over 100 seconds or so. The question I had, that?remained unanswered, is?what is it about the OTA that?is causing the?star drift, in an otherwise?Very well?guided mount.
I now have the answer. The main mirror is shifting within the OT. Evidence I'd collected,?indicated?that this?was?a?leading suspect, though?there were too many other possibilities and?unknowns to say so for sure. To put the question to bed, I finally decided to?drill and tap 5 of 1/4-20 holes in the OT, around the circumference, 72deg apart, in line with the outside edge of the main mirror. I then?turned?5 nylon screws in until?each?slightly snugged against?the edge?of the main?mirror. End result,?300 sec (5 min) images,?with a?standard guide?scope?setup, now?track "perfectly". By around 10 min,?some elongation is regularly?noticeable, but whether acceptable being a matter of taste.
|
George Dunham
