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I’ve been struggling with elongated stars for the past few months now and have tried numerous things and read through similar threads here and on other forums with no success. This is really starting to get to me as I’ve lost track of the number of clear nights wasted so far.
The elongation direction is not consistent at all and varies over different parts of the sky.
Mesu 200, Celestron RASA, 60mm StarGuider guidescope, QHY5L-II guidecam, Atik 414EX main imaging camera, Baader UFC, Baader F2 High Speed narrowband filters.
Things tried so far:
Tested for cable drag and recently started routing all cables coming off the scope at the back of the dovetail.
Both RA and DEC balance is spot on. This was performed several times with a digital fishing scale and the balance points marked.
I’ve always used SharpCap for PA but also tried several runs of PHD static and drift alignment with the same results.
Read the entire SiTech Operations manual for the Mesu as at one point I was getting elongation mostly in Ra and though the mount may not be tracking at a correct sidereal rate. There’s a method of calculating the proper track rate and have spent a couple of imaging sessions doing this with limited success. The method involves measuring the drift of a star in Ra in an interval of 10 minutes. Then after some clever math, one can change the Ra motor ticks in the ServoConfig configuration for the mount. This worked, but only for the position in the sky where the drift was measured and as soon as the mount was pointed to another part of the sky, the issue would immediately reappear. What’s worse is that the same tracking rate would no longer give round stars on a different night in the same position in the sky it did for the night before.
Short exposures of a minute or shorter in any position in the sky give perfectly round stars. This eliminates collimation, issues with the camera or any other optical element in the light path as I see it.
Differential flexure between the main scope and the guide scope is a non-factor as I get elongation during unguided exposures. Tried tweaking the settings in PHD2 thinking I might be able to guide it out. Results, again, vary depending on the night and position the scope is in. Sometimes guiding would give almost acceptable stars and some improvement over unguided and other times it would simply make matters worse.
Additionally, rotating the camera 90 degrees results in the direction of elongation being rotated as well. The camera is coupled to the front corrector plate via screw adapters which I simply can’t see flexing.
The only time I can get round stars is with the scope pointing near the Zenith.
I’m at a point now that the only thing making sense is flexure within the RASA or imaging train. I know the camera is tightly fixed to the corrector plate so there can’t be any play there. The only place where flexure could occur would be at the main RASA Losmandy mounting plate. The plate is screwed in to the front and back aluminium holders by four M5 screws I believe. Thought these might have loosened over time but after checking, they’re as tight as they’d go.
Not sure how solid a RASA should be and I didn’t really test or look at this when I got the scope as there was no need, but when fully mounted, the scope can be easily rocked by applying light pressure to the top mounting plate. This is not an issue with the Mesu head as it’s simply rock solid and can’t move it at all regardless of the force applied. At this point it’s all pointing to the scope/mounting plate flexing due to gravity as the scope is not exactly light. This could explain the odd behaviour throughout different parts of the sky as the scope is flexing in different directions.
Trying to determine if it is indeed the scope flexing, I’ve done some testing yesterday. Setup everything as usual during the day and focused on a brick wall roughly 30 meters away on a day with no wind. Mount was off and both axes were locked with the mount hooks, so mount tracking errors or movement would be eliminated this way. Started with 5 short consecutive exposures, then at 10 minute intervals another 5 exposures were taken until 40 minutes elapsed. Each set of 5 exposures were integrated in PI using an average combination with no normalisation or any pixel rejection algorithms. This was done with the scope on both the East and West side of the pier pointing at the same brick wall and with the mirror both locked and unlocked.
Combining these integrated images into GIFs and plotting the Ra and Dec orientation clearly shows considerable drift over the course of 40 minutes. As can be seen the drift is not purely in Ra or Dec, but a combination of both.
Mirror locked. Scope on East side of pier.
Mirror unlocked. Scope on East side of pier.
Mirror locked. Scope on West side of pier.
Mirror unlocked. Scope on West side of pier.
These next four GIFs show the result of pushing on the scope’s top mounting bar. The direction of movement when applying pressure on the scope is very similar to the direction of drift in the first two GIFs. If I’m not mistaken this would indicate that the RASA is indeed flexing/sagging due to gravity. The scope was purchased from FLO about two years ago. Would this be considered normal behaviour or am I just barking up the wrong tree here?
Mirror locked. Scope on East side of pier. Before and after pressure applied on scope mounting bar.
Mirror unlocked. Scope on East side of pier. Before and after pressure applied on scope mounting bar.
Mirror locked. Scope on West side of pier. Before and after pressure applied on scope mounting bar.
Mirror unlocked. Scope on West side of pier. Before and after pressure applied on scope mounting bar.
I find it hard to believe that the image should drift this much over the course of 40 mins, but then again, I may be wrong and this isn’t out of the ordinary???
Any help with this from the awesome and knowledgeable SGL comunity would be greatly appreciated as I’m simply out of ideas and things to try.
First post on here looking for some telescope buying advise. I've searched and seen some similar topics which have been very useful but thought i'd summarise and see what the experts think.
I'm looking at getting myself and my girlfriend a telescope as an anniversary gift. She's not scientifically minded at all but she really likes the aesthetic of the moon. The house is filled with 3D printed moon lamps, jewelry, cushion covers etc.. We're about to move into a new house in Forest Hill in SE London and the new house has a really large garden backing onto more gardens so quite sheltered from all street lights. We both said to eachother a telescope might be a nice thing to have in the new house and something we can enjoy together in the new garden.
I've got a budget of up to £200 but by no means want to spend that much if I'm paying for features we don't need or will use.
I've got some experience with a reflector scope that was my brothers. He got it years ago and we both obsessed over it for about a month and then once we'd seen the big planets and a few blurry distant clusters we got bored and it never got touched again. That was a 130mm DIA reflector (skywatcher I think). After the initial excitement, my overriding feeling towards it was it was not worth the faff! This was in dark Northumberland as well, not London.
I've tried to explain this to my girlfriend when we've talked about it and said if we don't want the faff we might have to invest in a Go to electric telescope. The logic being if its quicker and easier to see stuff, we'll use it more. I did get then quite excited reading reviews and trying to find second-hand goto scopes and it seems like something in my budget (or slightly pushed budget) is something like a Celestron SLT 127. (have seen second hand ones go for £250).
However having then done a bit of reading on here I think i've worked out that those cheaper Go-to's are still not that quick and simple to use, ultimately i'm I'm still only going to see fairly blurry planets and smudges of deep space clusters. I honestly don't think the girlfriend will be impressed and I'll probably get bored after a while too.
So I think I've come to the conclusion that I want to get a much smaller refractor that would be much more accessible for viewing the moon and would allow us to see a smudgy Saturn and Jupiter on clear nights. A smartphone camera holder would be a bonus too as it adds a simple feature that would keep us entertained for longer.
Do you think that's a fair approach or am I being a little too pessimistic about what I'm going to see? If so then what scopes could anyone recommend? Stepping down to a slightly lower budget there are so many more options and it's a bit bewildering.
Hi Guys, this is my first post so would like to say what a great resource this has been over the years. Any problem I've ever had the answer has been here. Until now.
Just wondering is anyone else having a problem with horizontal banding on the Atik Horizon. My high gain subs have terrible lines across them which is made worse by stacking. The lines are also present in low gain subs when stacked. See attached pic of 1 300s high gain image.
Hopefully it's just my camera and not a feature of the product.
I realise this can be a CMOS issue but surely Atik haven't released a product with this problem? Certainly not at this price?
After a 2 month wait, we finally got some clear slies last night so I had a chance to finally try out the Orion Starshoot autoguider.
Sadly, I spent a long and very frustrating night just trying to get the darn thing to guide properly, but wihout success. I was getting great tracking results from my HEQ5pro mount on its own, round stars on any exposures up to about 30 seconds, but as soon as I engaged the tracking scope, it was driving it all over the place (see attached pics).
I'm using the 50mm guidescope that comes in the "Orion Magnificent Mini" kit, and I made sure to enter the correct focal length (which I believe is 162mm) into the PHD2 software (not 50mm as I've read others have accidentally done ).
There was zero wind last night, so I can't really blame that. Everything seemed to be done-up tight, although I have just started using the HEQ5pro extension tube to avoid tripod leg collisions, which together with the Explore Scientific AR152 refractor scope, does make for a very tall setup, but I think I can discount that because it still tracks really well without the autoguider engaged.
A lot of the PHD2 tools and controls are a bit of an alien language to me, but I spent most of the night trying various settings and running some of the built in tools and following the reccomendataion, but to no avail, not even a slight improvement.
Does anyone have any ideas how to get this autoguider to work? Would really apprciate any pointers - ideally without abbreviations, as they'll just make my brain hurt even more that it already does
Much thanks in advance.
I'm new to the game. Bought a Celestron 102 for Christmas 6 years ago when I was in Louisiana. The winter nights usually never got colder than low 50s and were clear as a bell. I wanted to start locating and resolving binaries, but moved to Rockville MD and between the buildings and light pollution only set the scope up once. Now I'm in Washington state sorrunded by 100' cedars and clouds. I have enough distance from the trees North to see Polaris, but haven't found it yet through the glow Seattle cast through the haze. In Louisiana I had great views of Neptune, Jupiter, Venus. Last night looking just west of straight up with just my eyes I think I could see Vega fairly well. Anyhow I'm going to try to set up on my deck, but I'm worried about vibrations. The deck elevates me about 8' and gets me off a 20* grade. I have a little concrete patio but useing it it will put Polaris behind the trees and completely cut off my south and west horizon. I retire in a couple of weeks and want to spend some time learning this astronomy thing. Looking forward to learning. Oh I want to hook a camera to my MacBook. Anyhow thanks for letting me join.