pete_n_pugs

Thanks. I know the primary is covered in this pic, but this is about as good as I could get the secondary aligned (having moved the focuser tube since the secondary cannot be moved relative to the primary). I used the adjustment on the spider to get it as close as I could to centered left/right. Will have another go tomorrow. The OCAL is quite useful as it can at least take a picture - otherwise it's my phone which is rubbish!

Hello again, I have made progress... of sorts. I managed to move the focuser tube away from the primary - which should have the same effect as moving the secondary towards the primary, but not by enough to get it centered. I've been thinking about ways to get it actually central, but they would be quite mildly to quite drastic. I could make a different plate to hold the secondary, with the threads for the secondary adjusters further towards the primary, but currently the threads go through the spiders too, so the would need drilling or slotting appropriately. I could replace the entire spider and secondary holder with any adjustable one... For now I've decided to make do with what I've got. I have flocked the inside of the top part (not sure what it is called - that the trusses, focuser and spider attach to - the open frame), and I'm trying to make a shroud - all of which should help. However, I am now somewhat confused as to what I should be aiming for with my collimation, if the secondary is off center. Should I be adjusting for the primary to be in the center of the secondary, or the focuser tube. I went with the secondary - image below. I moved the yellow circle to be the outline of the secondary, got the primary (blue) in the center of that by adjusting the secondary, then adjusted to primary to get the purple cross on the center of the camera. This can be seen better in the second image (using a red led torch) to illuminate the camera. Is this almost collimated? I did get it slightly better, but rushed outside before taking another photo. As an aside, how would I collimate this in the dark? If I went to a dark site, the whole thing would need reassembling, so would need re-collimating. I'm guessing that this is where the laser collimator would come in handy? I tried using the OCAL with a red torch, and that seemed to be OK - is that an option? Thanks!

I've struggled to get anything resembling an airy disk, but that may well be due to lack of skill, and possibly seeing conditions. I'll also check the secondary holder. I want to enclose it and also move the mount points for the trusses anyway. Thanks all for the help so far.

It may be that I can adjust the distance to the primary by sliding the whole secondary having loosened the screws clamping it to the spider - if the holes were slotted. But I would need to remove the secondary to access the third screw - which would make the process of aligning very tedious as it can only be checked with the secondary reattached. Is it worth pursuing - or should I just make sure the secondary and primary are aligned?

This is one of the thumbwheels on the spider I am referring to, but on reflection (excuse the pun) I imagine it can only adjust it left to right, or towards and away from the focuser tube. Hopefully I am using the right nomenclature.

This might be clearer. I notice that the spider has thumbscrews - I'm guessing it might be possible to move the secondary with those?

Thanks for the thoughts so far - glad I'm not being too obtuse. Here is an image with card behind, and the primary obscured. Looking at the schematic above, do the outer two circles represent the focuser tube and the secondary?

I've read quite a few articles and watch videos, but I still can't quite get my head round it... I have a Explore Scientific Ultralight Dobsonian. This has two 'features' that I'm not entirely sure that I understand the impact of on collimation. Firstly there is no adjustment of the secondary up and down/along the primary axis. That is related I guess to the second item - the secondary is offset. So given those constraints, what should I be looking for in terms of alignment? I bought the Ocal collimator as I wanted to confirm the position of the secondary, and the Cheshire I have was confusing me as to where the secondary should appear. Attached is an image from the Ocal. Should the secondary be concentric with the focus tube? I should have taken another photo, but the red circle should be aligned to the focuser tube, and the green aligned on the outside of the secondary. When I properly checked collimation this week, the secondary seems to be offset from the center of the focuser tube. Is that expected? Adjusting the tilt of the secondary is the only option I have (although there is some possible adjustment in the spider - the implication in the manual is that this offset is set at the factory and should not be altered). Should adjusting that move the location of the secondary in the focuser tube? I will endeavour to get a better photo. The mirror doesn't seem to be perfectly round - is that what I need to adjust the tilt of the mirror for - to get it circular? And if it is off center by design, I can realign the crosshairs to the center of the secondary, and use that for the primary alignment. Perhaps I would be better off buying a decent quality laser collimator, but they don't seem to be in favour. Related to this, I tried to do a star test, but I've not been able to see any airy disks. I've a Baader zoom eyepiece, so perhaps I need to use the barlow as well? I can see a donut, with the 'hole' in the center is well centered either side of focus.

Thanks Geof. I'll see if I can work out how to change the ROI - gives me something to do with all the clouds around!

My second attempt, after completely over exposing on 10th Nov. Still learning the telescope (Explore Scientific 10" Ultra Light Dobsonian), the camera (ASI 533MC), and the software (SharpCap and AutoStakkert 3). Simple question, but since this is a Newtonian, should I flip the image? Any comments or suggestions to improve this appreciated, as I used default settings as much as possible. No Barlow used, next time! I was able to capture 1000 frames without needing to move the scope - Dobsonian so no tracking. Capture details (1000 frames) FrameType=Light Debayer Preview=On Pan=0 Tilt=0 Output Format=SER file (*.ser)(Auto) Binning=1 Capture Area=3008x3008 Colour Space=RAW8 Exposure/Gain Shift=0 Temperature=16.6 Hardware Binning=Off Turbo USB=100 Flip=None Frame Rate Limit=Maximum Gain=65 Exposure=31.4190ms Timestamp Frames=Off White Bal (B)=95 White Bal (R)=52 Brightness=1 Auto Exp Max Gain=300 Auto Exp Max Exp MS=30000 Auto Exp Target Brightness=100 Mono Bin=Off Mask over exposed pixels=Off Some details on the processing... Analyze Planet CoG, Dynamic Background Quality Estimation: Laplace, Noise robust (5), Normal range (local) Reference frame, Auto size Stacking: Grid AP I used 6% of the 1000 frames captured Sharpened Drizzle 1.5x I did find that the secondary had fogged up when I tried to take a second run. Can you use a dew heater on a Newtonian? I do need to add a shroud as well.

Thought I'd say hello as I've been lurking for a while. I've got a 130 flex tube, which I hadn't used for quite a while. That had prompted me to try astrophotography, but I failed at that, even with fairly decent kit (iOptron CEM25, WO ZS61, guiding etc). I was also suffering from lack of sleep due to staying up to try and get it all to work, then processing images. So I sold it on - which I do regret, but it was probably the right thing to do at the time. Fast forward a few years, and I got my dob out again, and had several really enjoyable nights looking at Jupiter and Pleiades. This prompted me to get some better eyepieces, then I ordered the Explore Scientific 'Ultralight' (its not really) 10" Dob. My plan is that I will stick to visual as I can (in theory) pop out for an hour or so, and actually see something in that time. I can also pack it all away reasonably quickly, and transport it to a better location relatively easily. I live in the middle of Windsor, with a small, walled garden with light pollution, but I'm still managing to enjoy myself, and look forward to going somewhere darker soon. I'm finding the forum a great resource, but need to resist the temptation to spend too long reading and not observing, and also not to succumb to GAS (gear accumulation syndrome). Any advice on the latter would be appreciated! I'm trying to focus on things that will make my viewing more enjoyable and less frustrating, but at the same time I want to learn to navigate the sky without resorting to a go to - yet. And I do want to do some imaging, but again I need to remember the frustration that can cause. Anyway, enough rambling for now!

I have a Panasonic GF1 - which is similar. I am just beginning but not being able to view the image on a laptop via USB for focusing, or to send to astronomy.net for plate solving is real pain. Not having a go to mount I had to make numerous trips with the SD card to check I was pointing in the right direction. I am also seeing a lot of sensor noise above ISO400, and what looks like amp glow. So depending on your budget, I would say £100 might be well spent - but it depends on what you are trying to do I guess. I am certainly considering that route, or saving up for a dedicated astro camera