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Astro Adj

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10 Good


About Astro Adj

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    Star Forming

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    Colchester, Essex, UK
  1. Thanks Ron. Actually I didn't need to hold the camera to the EP, I'm sure I'd never a picture of anything if that was the case! I've got an adapter that lets me attach the camera to the EP, and also a shutter release cable so that I don't send the image wobbling everywhere when I push the button! I think my scope is now collimated correctly, although won't know for certain until I can get back out there. I can't wait to try again when the scope is performing at its best! One thing that surprised me was how quickly the moon sped through my FOV, even with tracking on. I wondered if this was due to the speed of the moon being very different to the sidereal rate that the stars follow?
  2. I recently messed my scope's collimation up quite badly whilst trying to fix something that wasn't actually wrong! Rather than drive to my normal dark site I decided to take the dob out into the garden to see if the remedial adjustments I'd made had done the trick. The bad news is my collimation was horrible. I couldn't bring a star into focus, and mistook the double star Algieba for Saturn! The good news is that the moon, whilst not pin-sharp, seemed acceptable. I decided to attach my little 4MP digital camera to the EP via an adapter and take some images! The picture below is the best I could do, I found it hard to focus the image as the camera's screen is tiny and very low resolution. Nevertheless I was happy that it turned out okay. I'd definitely welcome any advice or tips as I am entirely new to this but would like to improve as I really enjoyed taking the images! Camera was a Nikon Coolpix 4300 in B&W mode. EP used was a 25mm plossl with a SW LPR filter attached. I used Picasa to tweak the picture (added a tiny bit of sharpness and increased the shadows very slightly) and correct the orientation. Right, I'm off to use my new colli cap to sort this scope out!
  3. Well, this is embarrassing. I decided to have a play with the scope last night under some decent lighting. Before I did anything I thought I would take a picture of the offending black line that was blocking part of the primary. I peered through the focuser, and reached up the side of the tube so that I could rest my finger on the lip of the OTA, directly above where the mysterious black line was. I then looked down the tube at the spot my finger was pointing to and proceeded to kick myself. Hard. Anyone like to guess what I saw? My shroud had become loose at the bottom and part of it had snuck in the gap between the top and bottom sections of the tube. As a result, when the scope was extended part of the shroud was left inside the tube, and obviously that part completely obscured the section of the primary it was above. Doh! I didn't have time to make any adjustments after that as something came up, but needless to say I felt like a bit of a wally. Then again, I learnt several new things about the art of collimation which will no doubt be of great use. I am actually looking forward to getting the HoTech out now! Oh, and while I was drilling the hole for my collimation cap I thought I'd also drill a small hole through my screwdriver's handle. I threaded a piece of lace through the hole and now I can keep it wrapped around my wrist when adjusting the secondary - no more nightmares about dropping the screwdriver onto the primary!
  4. I agree with Mick, and faced a similar buying decision recently! The only other consideration is whether the scope's size/weight is something you need to pay attention to? I couldn't fit the 300P into my room (well, technically I could, but it would have ended up going out of the window shortly after my wife saw it...) but ended up going for the Flextube version as it didn't dominate the bedroom when collapsed. If you can live with the bigger size, the 300P will reward you with what you can observe with it that wouldn't be possible in 250. In fact it can gather 44% more light than the 250!
  5. Mick, I think Mars was disappointing because of the poor conditions. I'm not sure how to describe it, but whereas the site I was at usually has a limiting magnitude of around 5.5 on this occasion I struggled to see the 3 stars that make up Orion's belt! At this point there were no clouds in the sky, I can only assume it was mist or something similar. Mars actually gave some detail (a dark scar slightly northwest of its equator) but I couldn't bring it into any sort of focus. As a rule of thumb, though, how long should I allow for the scope to cool? I usually leave between 30 and 40 minutes depending on the difference between the car and ambient temperature. I have also taken to driving to the site with all the windows open! Mark, yes, that does make sense. I've not tried to see if the laser is centered on the secondary (both immediately after it leaves the HoTech and on its return journey) but would I do this by using a small mirror to look at the underside of the primary? If so, at which point would I pop this step into my routine? Would I check and adjust (if necessary) at the same time I perform the check advised by Mick? (Rotate the secondary until all 3 primary mirror clips are visible and the secondary is a circle in the centre of the image through the colli cap). Thanks for the tip!
  6. Thanks Mick. Actually that's almost exactly what happened - I took the scope out but after about 10 minutes the sky clouded over. I wasn't happy with the views I had of Mars during those 10 minutes so decided to investigate, which prompted a lot of messing around after I realised only one primary clip was visible. Thing is I wasn't really sure what to change so tried all sorts, my thinking being that if I turned a screw the wrong way I could always turn it back again! I think I'll have another go at home tonight with the colli cap. If it seems okay I'll deliberately mess the alignment up then start again, and repeat until I've got the hang of it. Ironically I thought I already had it sussed, and was so pleased with the HoTech because it made the process quick and painless. Just goes to show clever tech is useless unless the operator knows what information is going in and what should be coming out! What benefit would a cheshire collimator bring to the party? Does it perform the same job as the colli cap but with greater accuracy or is it used for a different stage of the collimation process? One other question, do you unlock the primary locking screws before adjusting that, then tighten them once you've finished? I've never actually used them!
  7. Thank you both for the suggestions. I do not have a collimation cap, so that will be my first port of call. I love the idea of using the blank - I actually have 2 (one for the 1.25" adapter and one for the 2" adapter) so I'll use one of them as a colli cap and the other as my dust cap. Once this is on the focuser, and I've loosened the centre screw and the 3 adjustment screws, is it then a matter of looking through the hole in the colli cap and rotating the secondary until all three clips are visible? From this point should I commence my routine or is there anything else I need to be aware of? I understood from reading some articles on collimation that before I adjust the 3 screws on the secondary I should first ensure the secondary is in the right place by loosening the centre screw and moving it up and down the tube. Is this necessary or is rotating the secondary enough? Mick, do you tend to collimate every session? I am doing this currently but have read that actually the secondary should hold its alignment reasonably well for some time. I just wondered if I am fiddling with it unnecessarily. Thanks again for the help!
  8. I've recently bought HoTech's SCA laser collimator after reading lots of very positive reviews. It seemed like a good match to my 12" dob as it meant that, in theory, I should be able to collimate it accurately and quickly all by myself. Unfortunately I think something is going awry. After I have finished my collimation routine the laser is in the middle of the donut on the primary, and the reflected laser is exactly in the middle of the grid on the side of the HoTech. Just to go over the steps quickly (in case I've missed something), here is my routine: 1/ Insert 2" adapter into focuser, insert HoTech into this. 2/ Tighten HoTech until I am unable to rotate the compression ring any longer (I assume this means the SCA has done its thing and centered the laser in my focuser) 3/ Switch laser on and look at the donut on the primary to see how far out the laser is 4/ Adjust the 3 allen key bolts until the laser is dead centre on the donut (note: I have noticed that the 3 bolts are all relatively loose to achieve this) 5/ Go to the end of the scope, and look at the laser grid on the side of the HoTech. 6/ Adjust the primary mirror (using the 3 knobs) until the reflected dot is bang in the middle of the targeting grid. In fact the dot 'disappears' in the middle of the grid - I can only see the crosshair surrounding it. 7/ Return to the secondary mirror and make any adjustments to re-centre the laser in the donut if necessary. 8/ Turn the HoTech off and remove the device. However, when I do star tests and pull the star out of focus instead of seeing concentric circles I end up with a flat edge across the image. If you look at the letter 'C' and draw a line between the two 'ends' it will look similar to what I'm trying to describe. I then decided to peer down the focuser, expecting to be able to see the 3 primary mirror clips. However, I could only see one, and directly opposite the clip I could see was the same black line cutting off the rest of the circle. I've edited a picture from Astro Baby's excellent article on collimation (I hope she doesn't mind - really should have asked first) and attached it below. I'm pretty sure this is not right. My thoughts are I've either done something wrong, the HoTech is not completely accurate or I have a more serious problem with the mirror itself. After spending a lot of time researching collimation I have noticed there are a few things I do NOT do, namely: 1/ Use the central screw on the secondary to move it up and down 2/ Use the locking screws on the primary 3/ Use a system of 'loosen one, tighten the opposite' when adjusting the secondary - I tend to move to each one in turn and try turning it CW, then CCW and see which direction moves the laser closer to the centre of the donut. I get each one as close as I can then move onto the next screw. Could one/all of the above be the problem? If not, can anyone help me find a solution? Thanks everyone.
  9. Do you know which RDF you have? My old Skywatcher scope came with one and I could help you adjust that...I wouldn't be sure about other models though! On mine there are 3 small knobs that can be turned. One is an on/off control (also allows you to increase/decrease the intensity of the red dot), and the other 2 are the adjustment knobs. One is for vertical adjustment, the other horizontal. If it helps, on mine one of the knobs is underneath the back of the RDF's body, the other is on the right-hand side, near the end of the RDF. Once you've found the adjustment controls, it's just a matter of fine-tuning the alignment. I start with an object like a chimney or tree that is a good distance away, and make sure that when the object (or, more likely, a specific part of that object) is centered in my eyepiece the red dot is placed on the exact same part of the object. After the daytime alignment I repeat the process on a star - the daytime alignment should be sufficient to get the star in your eyepiece's FOV, and from there you can make the tiny adjustments required to get the RDF directly on it when the star is centered. I find decreasing the brightness helps me to see exactly when the red dot is on top of star. Hope this helps a little.
  10. Thanks for the link. It appears they have sold out, but I've bookmarked the site and will check back frequently. In the meantime I am going to go to work on the edge of the secondary with a Sharpie!
  11. Thanks for all the replies, everyone. I've had a think about it and am going to invest in a QuikFinder. Although it means I'll be going without the extra circle, the fact it is at an acceptable height without requiring a riser and is more resistant to the nasty machinations of the dew monster sealed the deal. Eventually I would like to have it beside a RA finder, just as Mike has. I think that, combined with a Wixey and a azimuth circle should really make a difference to my observing sessions. Thanks again for the help, I expect I'll receive the QuikFinder and Wixey within the next couple of days (FLO's delivery speed is amazing) so I'll be sure to include my experiences as soon as I get some clear skies.
  12. Thanks for the advice. I hadn't thought about the profile of the finder, but now that you mention it one of the problems with my current finder is that it is quite close to the OTA which can make it awkward to look through. As such I guess the Quikfinder would be better in this respect. I understand the idea of the Telrad is that you can use the degree circles to hop accurately to an object, so if an object was 10 degrees away from a specific star or other object you could make two 4 degree jumps followed by a 2 degree jump. But does that work in practice? I was thinking I would be more likely to just centre the object I was planning to observe in the 1/2 degree circle then use the telescope with a low-power EP from there. In this case, though, would I be better with a simple RDF?
  13. Mick to the rescue again! I have added this to the list of 'things I need to do to my dob'! Thanks for the link.
  14. I am in desperate need of a zero magnification finder for my dob, and both the Telrad and Quikfinder seem like superb bits of kit. I was just wondering if anyone has an opinion as to which is better? As far as I can tell, the Telrad has an extra circle (4 degrees) but is heavier. Are there any other differences? Would both finders slot into the baseplate that is currently occupied by my (mostly useless) straight through finder? Or would I need to do any drilling etc to mount either one? They both seem to be around the same price (£35-£40) so I'm currently leaning towards the Telrad. But I would greatly appreciate some thoughts from anyone who has owned one or the other (or, perhaps, both!). Thanks everyone.
  15. Chris, is there a particularly set of filters you would recommend? The price for a set seems to vary enormously! Stuart, excellent work! That gives me some hope, I'll have a go at clicking (agree that sounds more agreeable than stabbing!) next time the clouds part for any period of time. Twotter, that EP looks identical to a Meade 32mm EP that I use currently. It also has the same AFOV - 52 degrees - which in my scope gives a TFOV of around 1.11 degrees. In my old scope it produced a TFOV of around 2.56 degrees, which was much better for viewing M31. The problem I have is if I go much more than 32mm I start to have an exit pupil figure of more than 7mm, which isn't recommended. The only solution I can see is to invest in an EP with a bigger AFOV (you can get up to 100 degrees now!). Andrew, thanks for the link. I read that thread and am definitely going to copy your modifications. Could I ask where you obtained the flocking paper from? I've found some suppliers based in the US but none here unfortunately. Would you be able to point me in the right direction?
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