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Posts posted by alacant
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Hi and welcome
Astro in Spain is exhausting. Just pray for cloud so you can occasionally get a good night's sleep 💤
Cheers
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8 minutes ago, TiffsAndAstro said:
measure with a micrometer, mark with chalk, cut with axe
No, no. You must not do that. Chalk makes dust which could get onto your lens.
Otherwise, good advice😉
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22 hours ago, DeCosta said:
taking the camera back to the UK
Hi
In Spain, maybe call Luis at str-astrum who may be more knowledgeable as to your climatic conditions.FWIW, for cooled CMOS here in Alicante, we've standardised on -5º all year round. In summer it's not easy maintaining much below -10º anyway and the benefit it brings is negligible.
HTH -
Hi
I don't think a change of glass will make much difference, but a triplet may.
Ideas. Use a:
- focus mask to get you close to focus, then remove it. Use live view to move away from that focus point until the blue halo is reduced.
- reflector
- #8 and correct the colour cast afterwards
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2 hours ago, Andy56 said:
Siril batch Banding Reduction on these files to get a new set of FITs
Hi
Siril flips the images.
Is there any reason for not using Siril to process your cr2s from start to finish?
Siril's banding algorithm is best applied after pre processing the fit sequence. You need only a flat frame stack which has had the offset subtracted.
Details here.
You are free of course to flip back or choose any orientation you like. Probably easier though to do it after processing.
HTH
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Hi everyone
First night for ages I had a telescope to myself. In fact two. Cheepo specials; a gso203 and a Bresser 203.m106, ngc2903, m63 and m66, changing to the gso after 106. Forgot to take flat frames, so had to guess the camera angle for the Bresser. Hopeless. The only way out was graX's AI, which I really don't like. Ironically, I think it has the best background.
Thanks for looking.
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5 hours ago, TiffsAndAstro said:
It's probably something that could be sorted in 5 mins in person
Hi
Some stuff is difficult or impossible to describe in words on a forum.
The in person person is at your local astro club. Any of the members would be only too willing to get you polar aligned and imaging. Probably in less than 5 minutes!
Cheers
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1 hour ago, TiffsAndAstro said:
don't think i saw anything about trying iso800
To reseat the front element, simply loosen its retaining ring until upon shaking the lens, you can hear it rattle. Now tighten the ring until the rattle just disappears. That should help with the astigmatism/gulls/birds.
ISO800 is the optimum setting for low noise on the 18mp sensor.
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4 hours ago, TiffsAndAstro said:
tried stopping down to f5.6
As per our 700d -same sensor- and an old Takumar 135... Did you try the ISO800 5s f8 no drizzle idea?
You might also try loosening and reseating the front lens element.
Cheers
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18 hours ago, mikeDnight said:
What's the point of the Bortle scale?
People seem obsessed with it. I image. To me, it's useless. Where I live, I can see the milky way. But if there's a moon, haze or I've been looking at my 'phone, I can't. I don't need a number to associate with these observations.
But... Is it a 'good' night if I can see the milky way? No idea until I've assessed the seeing. If it's poor, no amount of Bortle is going to change it.
Cheers and clear skies.- 4
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17 minutes ago, Elp said:
F10?
I suggested f8:
50/6 = 8 and a bit -
1 minute ago, Elp said:
Or use step down rings
Really? A step down ring to 6mm?
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9 hours ago, TiffsAndAstro said:
why would i place that over the front of a lens ?
It gives you a circular aperture, helping control aberrations around stars, particularly those caused by the non circular edge of the lens diaphragm.
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52 minutes ago, Kon said:
Is it advisable
Hi
No need to cut the spring. Simply remove it. That should give you the distance you need.
To help you with the secondary, replace the hexagonal grub screw adjusters with M4 hex head bolts; much easier to take up the slack that way.
HTH
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25 minutes ago, Kon said:
For my 12" (f5) i should have the offset (fast).
Yes. My bad. I read that the 8" was f5 and the 12" f6. f5 is offset. f6 is much more central.
But the method I gave to adjust the secondary is still correct; the secondary is both too far toward the primary and is rotated incorrectly.Cheers
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1 hour ago, Kon said:
it seems to be a secondary
Hi
The main difference between f5 and f6 is that for the latter, you'll find the primary donut reflection will collimate almost centrally, with very little offset.
You have it set (perhaps by habit?) more as if it were at f5. Primary visibility is not helped by the small secondaries fitted to sw Dobsonians. The fix is easy:1. Move the secondary toward the open end of the tube a few mm. To do this, loosen the three secondary adjusters and turn the central screw clockwise.
2. With the secondary adjustment screws still loose, rotate the secondary until it appears circular. Relative to your photos, you'll need to rotate the secondary anti-clockwise.Repeat 1 and 2 until you can see the missing primary mirror clip. Now you will be able to complete the collimation
Focuser? Be sure to read the common collimation myths and Seronik's no nonsense collimation guide.Note that the fast and slow photographs in the AstroBaby guide are incorectly labelled. They should be like this
(you're aiming for the slow version):fast:
slow:
Cheers and HTH
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4 minutes ago, v4169sgr said:
I estimate 56-57 mm between the image plane and the M48 thread.
Therefore, and as your images show, apart from tilt, you are too close. Can't recall exactly but we needed at least 58mm from the shoulder of the m48 thread. The m48 t-ring alone will give you 55mm. With your 2mm spacers that's probably around 57mm, but you're now at the safe thread limit. Baader give 57.5mm. Use 58mm as a starting point. The low profile t-adapter with a set of extension rings makes this easy.
9 minutes ago, v4169sgr said:is it really legitimate that the MPCC II doesn't remove all the coma
It removes the coma, but introduces astigmatism. If you want out-of-the-box-corner-to-corner over aps-c, perhaps consider the GPU.
Cheers and HTH
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11 hours ago, v4169sgr said:
software
Hi
If you're able to reach focus with the clicklock, then it looks just about as good as you're gonna get. If not, use a low profile eos-m48 adapter and a 12mm extension tube.
The tilt was measured using Siril under Ubuntu 22.04.3. The same version will run under Mint but if you're interested in the journey as much as the destination, you may wish to build the latest version from source. Testing and reporting bugs helps the developers toward the next release.
HTH -
On 13/02/2024 at 22:02, v4169sgr said:
Is there any improvement in the second image
Hi
Excellent shots, but if you feel you want to take it further...
Both images are tilted; make sure that the primary mirror is adjusted correctly and ensure that the camera-cc assembly be inserted correctly into the focuser.
Baader cc? Lose the m42 adapter and go with 58mm from the m48 shoulder. If your focuser has a compression ring, avoid clamping across the shoulder of the undercut of the cc. Or just remove the compression ring. Simply dismantling and re-seating usually helps.But hey, 450d on a 200 f5; if you're satisfied with the images perhaps stay as you are.
Cheers and HTH -
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2 hours ago, Spad said:
I have a Sky-Watcher Explorer
Hi. What's wrong with it? What are you expecting over and above that which the 150 offers?
Cheers
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Weird interference that occurs 1-2 secs after opening image - Canon 600D
in Discussions - Cameras
Posted
Hi and welcome
Llinks to each cr2 may help us diagnose.
Cheers