Stub Mandrel
-
Posts
10,662 -
Joined
-
Last visited
-
Days Won
32
Content Type
Profiles
Forums
Gallery
Events
Blogs
Posts posted by Stub Mandrel
-
-
Good stuff!
-
1
-
-
24 minutes ago, Maho said:
Just ordered my 130 PDS (first scope)and I cant wait!! Really excited.
Any idea where I can get a t ring for Olympus EM10 m2 t ring?
Here's one, there will be cheaper on eBay I guess.
-
1
-
-
On 26/07/2020 at 12:40, Jack Jack said:
MPCC Mk3 which helped but not across the whole field
They are very fussy about spacing, try moving it outwards in steps of 0.5 to 1mm, if the coma is more or less away from the centre.
A small amount of tilt will become insignificant when adjusted spot on.
-
1
-
-
On 21/07/2020 at 21:24, cuivenion said:
measure the tilt.
You could use a depth micrometer or the tail end of digital calipers to measure how high the lip is compared to the surround. Obviously the paint finish will limit the accuracy.
-
On 17/07/2020 at 16:48, Heskyyyyy said:
Bode's Galaxy. Avoiding Polaris as an alignment star was extremely wise, as I was able to get all 15 second exposures (ISO 1600) with minimal to zero trailing. 71 subs. Target was to the North, so I couldn't really get rid of the blue background, or maybe I'm just bad at processing 😛
Hi, hope you don't mind, I took a screen grab of your image and pasted it as an image in Photoshop.
I cropped off the dotted line, created a mask to exclude the galaxy and ran gradient exterminator. This balanced the background colour to a neutral dark grey.
Then I applied a flattened S-shaped curve to brighten the faint parts fo the galaxy (but not the very darkest bits) while not blowing out the stars. You need to experiment.
Then I ran an 'increase star colour' action 2 or 3 times.
It coudl do with noise reduction and tweaking to smooth the background, but you get the idea.
It's worth you persevering with your original data, 99% of the hard work is processing!
-
I think I'll have a go at my unconventional 'floating mod'... kill or cure!
-
17 hours ago, michael8554 said:
Wrong I'm afraid.
Autofocus becomes incorrect once the #LPF2 filter is removed.
Autofocus assumes the sensor is in the factory position, but removing the #LPF2 filter has the same effect as if the sensor was moved further from the lens.
Autofocus is corrected by removing shims to move the sensor closer to the lens.
Or screwing in the Torx screws on newer Floating Sensor models.
As I thought, Merlin has managed to correct with a Clip-In filter.
Michael
Sorry Michael,
The autofocus mechanism is all before the mirror; removing the internal filter does not affect the autofocus mechanism. This is the fundamental reason why you need to make a correction.
You said a clip filter could work - it most definitely won't help with autofocus.
I've found the Baader filters and they are too costly given the risk of breaking the camera.
My main question stands... what distance do I need to reduce the shims by - not having the original filter I can't estimate it and the only figure I could find assumed a thinner filter was used to replace it..
... but I've been given an idea by this discussion: slightly reduce the height of the mounting pillars, insert a rubber grommet, and treat as a 'floating' sensor adjusted by trial and error.
-
26 minutes ago, michael8554 said:
Isn't that the objective...... ?
Michael
No... the autofocus isn't affected by removing the sensor glass as it uses the image reflected up to the pentaprism.
If you use a clip filter the focus point will change to compensate so the sensor image will still be out, compensating glass needs to be behind the mirror.
-
1 hour ago, MarkAR said:
Super images, green looks better I think, maybe the red is a little over saturated.
I will revisit them both, but in a few days with fresh eyes.
-
2
-
-
7 hours ago, michael8554 said:
Restoring Autofocus involves reducing the spacing between the sensor and the lens, not adding more.
Good point... it need to be a=bout 1/3 of the filter thickness, can anyone tell me what that is?
7 hours ago, michael8554 said:Some say that a Clip-In filter compensates.
I doubt it as it would be in front of the mirror and affect the autofocus as well. It needs to be behind the mirror.
Hmm.. problem with a filter is that for another £20-30 I could get an unmodified one..
-
1 hour ago, cuivenion said:
Is there a guide to adjusting tilt in the 130pds focuser?
There are three pairs of screws around the base of the focuser. Loosen the larger locking screw and tighten or loosen the small adjuster and re-tighten the locking screw.
If you do this with cheshire eyepiece you have eliminated tilt when it maintains collimation throughout the movement of the focuser. Tilt should show as the mirror centre spot drifting away from the middle of the view as you move the focuser over its whole range.
-
2
-
-
Portrait version with just 30 subs.
-
I prefer this to my close up image, it's a stack of 99 4-second exposures using a nice Zeiss 135mm lens. I deliberately left the gradient in
-
6
-
-
I've got and 1100D, astromodded, that I use for wide angle imaging, meteor hunting etc.
I dind't do the mod myself and like the 450D I did do, it hasn't had a spacer or extra filter put in.
I fancy using it for some ordinary photography as well, so I'd like to add the sensor spacers or an aftermarket filter to restore autofocus
Can anyone recommend a filter that fits over the sensor that won't ruin the Ha response and/or tell me the thickness of spacer I need to add?
-
Have
19 minutes ago, matt_baker said:This scope has served me very well but ever since I've acquired my 1600MM + filter wheel, it's been causing me a lot of trouble regarding tilt and bad stars.
I tried to get around this by purchasing this item which claims to reduce the tilt, which it does, only very marginally compared to just three thumb screws. In the description of the item, it stated that it can be rotated with a counter ring. Although this does work, it doesn't hold it tightly enough and causes even more tilt than there already was, and again, probably something to do with the weight as I was very easily able to move the camera up and down.
I have three options to amend my situation.
1. I can try to think of something else to completely reduce the tilt enough for it to be acceptable. I was thinking of a baader clicklock but I've heard it doesn't work on the stock SW focuser
2. I buy a Moonlite CR2 focuser. Only issue I'm not sure about is the added weight of the focuser + the camera and filter wheel means that I won't be able to balance properly due to the focuser hitting the tube rings of the scope
3. I upgrade and buy something like an Esprit 80ED.
Saying this, I really do like the 130PDS. It's fast, has wide aperture and a decent focal length for a dirt cheap price. I also appreciate the challenges that comes with a newtonian and the rewards it reaps if everything goes right.
The item I tried: https://www.teleskop-express.de/shop/product_info.php/info/p5417_Lacerta-Thread-Adapter-for-using--Baader-MPCC-with-Skywatcher-Newtonians.html
Have you tried adjusting the focuser tilt?
-
Last night's data. 12 5 minute subs each of Ha, OIII and SII. ED66, OVO flattener and ASI1600, Baader 7nm filters.
-
23
-
-
Looked great in my Celestron Nature 8x42 bins last night. I saw M32 near m31 with them as well.
-
Certainly too big for a 400mm scope! I won;'t relate all the problems I had but worst of all was forgetting I needed an extra spaced between the EFW and the flattener. Turns out my Coma Corrector one doesn't fit so hopefully I can print a stop gap... but somehow I need to find my 123mm lens!
-
5
-
-
On 09/07/2020 at 17:08, Heskyyyyy said:
From what I've done so far, yes 15 seconds, and still a bit of trailing in some frames. Might try 10 seconds instead. I have a 6se, 1500mm
That's a very long focal length for Alt-Az imaging... might be some sort of record!
-
Saturday night's subs, afflicted by the curse.
Previously this has been put down to walking noise (gradual drift of the images across the sensor) but I am convinced its caused by thin cloud.
Dithering is often suggested as a cure.
I am convinced it can't drift as the first and last subs differ in position by only about a quarter of the length of the streaks.
I haven't seen it with the ASI1600 before, and whatever the cause it seems always to be associated with poor transparency.
Still the jury is out.
-
I will be interested to see what difference 16-bits make under UK skies.
-
Lots of really nice Neowise images n here! I had given up on a decent comet!
I can't see the horizon from my garden, so after setting up a final run I walked about a quarter of a mile to a nice spot by a lake with my bridge camera and a tripod.
Was surprised to find the comet so easily, and for it to have an obvious tail!
I tried various things with my bridge camera. Luckily it has full manual overide including focus, but the longest exposure of 8 seconds gave a blur, but I managed some shots using different modes, 1 second is enough at ISO 800 even at ~1000mm equivalent.
These are stack jpegs, one is just three frames, two is six, stacked manually. The last one is eleven frames in high ISO mono mode, stacked in DSS. Stretched further the noise becomes overwhelming. Hope to have another go with proper astro gear!
-
4
-
-
I managed a test last night, this is an edit of my post in the 'what are you doing tonight' thread after sleeping on it.
Main conclusion- too much stiction on the dob part, I need to make it smoother! Not really an issue with the platform, I think I need to dose it with silicon polish at the very least. It moves in jumps and the minimum AZ move is often nearly a full FOV at ~30mm and getting a target centred at 5mm took forever! Alt is much better but not perfect, although if unbalanced it can move on its own.
As for the platform, PA was easy, at least to the suggested approach of getting Polaris in the finder and adjusting until it stayed still during a slew. The polar angle must be pretty accurate as I just set everything level and the task was setting it due north. Errors were rapidly apparent so a button to stop the slew early will be welcome. My finder's cross hairs come out at 45 degrees but that didn't make the process difficult. Better PA could be achieved with a polarscope in the finder holder and getting Polaris to travel around the circle.
Getting the track rate was hard. A first everything drifted off top left regardless of speed. This made me think it was running too slow. I reduced the delay down to about 15ms until the stars definitely went off the right side pretty sharpish. I then increased the delay, and eventually settled on about 64 milliseconds delay by the time clouds came in, which isn't bad given the estimate was ~68 and expected to need to speed up to allow for compression of the roller. I think the earlier problem was using Lyra which was very high and I suspect a combination of PA error and an unbalanced scope slowly moving in ALT when near vertical.
It was easiest to judge movement using small stars near the edge of the FOV rather than bright ones at the centre. Next time I will use a 25mm plossl with cross hairs.
Incidentally I used a Szentmartoni EP made according to a recipe on SGL that uses three small binocular objectives for about 33mm. As promised it was sharp to the edge and comfortable to use!
I changed to a Skywatcher UWA 5mm to 'fine tune' the tracking rate. the sky wasn't very dark, but I went back and (just) split the double double at 300X - seeing wasn't brilliant, but it seemed to be keeping in place even at that magnification, certainly long enough for planetary imaging.
Changes needed:
I will wire the disabled reset button on the shield across the end limit switch. This will provide a way of interrupting a polar alignment slew, as initial drift is obvious in a couple of seconds, you don't need to wait for a full slew.
I will round the default track speeds 0.1ms and keep the adjustment step of 0.1ms. The 0.1ms seems fine enough and it's annoying that all the readouts are not round numbers - and no point reading the delay to finer resolution than the adjustment. I may change the step to 0.05ms, at the expense of slowing down the tuning process a little.
Although up to speed up tracking and down to slow it seemed logical, as up increases the delay and vice versa. It's confusing to press up and see a number decrease.
The debounce period for the buttons is too long, as are some of the 'confirmation delays' of 1s. I will reduce both.
The 'nudge RA' increment was WAY too aggressive, the briefest of presses and the view changes completely.
A remote handset might be a useful addition, perhaps with a reduced set of controls.
Mechanically, everything worked fine with the platform. Balance is great and I didn't even bother with a nut on the pivot bolt for the dob, so worth considering a plain pin instead. There is some wobble when moving the scope, but it isn't excessive and I didn't notice any when hands-off.
Main beef is with the dob itself, I must find a way of reducing 'stiction' and counter-intuitively locking the alt movement. But my brain is already thinking of ways to add steppers and belt drive to ALT and AZ - perhaps for 2021!
-
4
-
-
Good, but could have been 20-30 minutes shorter!
-
1
-
Western Veil, narrowband
in Imaging - Deep Sky
Posted · Edited by Stub Mandrel
Hopefully this is the start of a new mosaic.
My new 33mm spacer seems to have come up a bit short as there some poor star shapes in the corners. Printing a new spacer an extra 0.5mm thick.
Really not sure what's right. The lovely green bit at bottom left in the first image seems to be an artefact. I still can't get a 'muddy yellow' in my hubble...
I'm interested in which colours folks prefer, and why.