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mint_mark

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Everything posted by mint_mark

  1. There are a few places that rent camera lenses like this. I was quite excited at Christmas to rent a particular wide angle lens to use with a CLS filter on my astrotrac. The company did two weeks for the price of one at Christmas to avoid any postal delays. The rental price included insurance. The packaging was very robust and easy to repack for return. The box probably does get replaced now and again for wear and tear. I had to pay postage both ways and it had to be tracked and insured. They had a calendar based booking system for popular lenses. As part of the deal they encouraged you to write a review of the item afterwards, which is a nice idea. I liked the lens, but had two weeks of solid cloudy weather. Will there be a discount for that?
  2. I think the key thing about the 1100D is that it's 12Mpixel and can go to ISO6400. That's a new combination for Canon and the hope is that the lower pixel density (lower than 18MPixel that is) will given cleaner images. The last 12Mpixel camera could only go to ISO1600. Of course, the new 600D has an articulated screen which is also a useful astro feature... and they are both lighter than the 60D which is another advantage.
  3. Well, I'm happy that I made a lucky guess about the integrated guiding, but it looks like I got the size wrong! It's not going to fit on my Manfrotto tripod is it... Does anyone know if it can do goto? Some nights it takes ages to find my target...
  4. Hi David, The blue colour is normal with the CLS filter. You'll also find that you have to expose for a bit longer too. Since you mentioned DSS, you can get it to correct the colour as part of the stacking process. On the "Light" tab of the "Stacking Parameters" window there is a background calibration option (at the bottom left). If you set it to "RGB Channels" then DSS will normalise the three channels to the same value, giving a grey background. Then when you play with the levels you should find some red stars in the area of M31... Sara, I bought a CLS filter and I've used it with my unmodified 1000D and 60D cameras. To try and describe the effect it has... by cutting down the sky glow it allows (or requires) me to expose for longer and capture fainter detail than I otherwise could. Also, I can attempt targets in brighter parts of the sky and nearer the horizon. I'm waiting for them to bring one out that can see through clouds
  5. I tried a similar arrangement with a monopod. I got the binoculars above me by resting the monopod on the top of a handy garden wall (about one foot high). The problem is that for higher elevations you still have to bend your neck back to look up, but at least it supports the weight of the binoculars. Next time I'll try the reclining chair and the monopod...
  6. Seeing this picture of the bar with two cameras... it made me think about getting a clamp and basically using a camera with a small lens as the counterweight for my (small) telescope. Then I could do widefield and longer focal length at the same time. I was wondering whether the shutter activation from one camera might cause vibration of the other camera... do you have to synchronise the exposures for both cameras? I guess the shorter the focal length the less it matters.
  7. I started with the tripod setup and then bought the wedge. And then the head when I wanted to mount my megrez 72. But with that setup (focal length 430mm) I have done 3 minute exposures after careful alignment. There are some things you have to check (and correct) to get good alignment... the reticle in the polar scope needs to be central in the scope and the scope holder arm might need adjusting to make the scope parallel to the astrotrac axis (I did this with bits of sticky tape). Other issues with long focal lengths... an unbalanced heavy load can be unwieldy (depending where it's pointing) and puts the astrotrac bearing under a lot of strain... the bearing can loosen over time. It's hard to make fine framing adjustments with a basic ball head... a better ball head with a tension setting helps. A geared head is good but might not move where you want it to go. I bought the astrotrac head so that the load is balanced. So yes, the astrotrac can handle it but it takes a bit of messing about... Mark
  8. You can double check and look through the viewfinder as well to see if you can see the star there. Other than that, my theory is that you were out of focus enough that the star was too diffuse to be visible. I don't know if the 450D does "exposure simulation" for its live view... you can try cranking the ISO up to max to see if anything appears then. I have to do that with my 1000D... ISO1600 for focussing and then back down again for exposing.
  9. Alright, I hope that this mount might fulfil the role of "smallest high precision auto-guided" mount. I hope for something small and portable, yet able to achieve longer exposures than the astrotrac and remove the reliance on ultra-precise polar alignment. If I'm dreaming, then maybe a mount with an integrated guidescope and auto-guider, if you can imagine such a thing.
  10. OK, I just wanted to complete the tests in this thread... I did buy the skywatcher flattener and had a chance to try it out. Here is the result... This is the top left corner of a 3 minute exposure at ISO 1600 through an Astronomik CLS filter. I think this is a big improvement on the WO flattener III. It's not perfect, but at least the stars are oval and not cross shaped This flattener doesn't reduce, so I am at f/6 and have to expose for longer, but I seem to have managed 3 minutes which I'm also pretty pleased with. Thanks everyone for your suggestions and advice... my next upgrade might be a new camera with a better LCD, so I hope to improve my focus accuracy. Mark
  11. I've got the Megrez 72 and I use it for imaging with a DSLR mounted on an astrotrac. It's the only telescope I've used like this and I find it very capable. The William Optics flattener III is very sensitive to focus. Even with good focus you do not get round stars in the corners of an APS-C sensor. I wrote a thread about it... http://stargazerslounge.com/equipment-discussion/112548-best-flattener-william-optics-megrez-72-a.html I need to update that thread because I have since bought the Skywatcher flattener and it gives much better results. It does not reduce the focal length though, so you are back to 430mm f/6. I have the original focuser and reading the previous responses here I would have to agree with them. If I have a barlow, extension tube and camera then it almost doubles the length of the setup. I'm sure there is some sag in the focuser and you have to get the tension just right to avoid it slipping with all that stuff in there. I'm thinking of getting a heavier camera so this might become more of an issue for me. Also, the focus lock knob causes the focus to change as you tighten it. You just have to compensate for that. I only found out about the new focuser from this thread, so I don't know if it addresses these issues. The little mounting foot is very short and nowhere near under the point of front to back balance (which is under the focuser end of the tube), so you need some way of mounting it back there. Other than that I think it's great and I'm glad I bought it.
  12. I would say that both viewfinder (with or without angle finder) and live view are both only useful when there is a bright object in the frame. When there is a bright object then I find live view very useful for focusing. Without it I think I would have to do small adjustments, test shots and review on the screen (and zoom in). I usually focus on a planet or bright star using live view before finding my intended target. When I am framing my actual photograph I always do test shots. Sometimes the targets are faint enough that they only show in a longer exposure at maximum ISO. I recently had to do 1 minute test shots just to find and frame the target. In summary, I would say live view is very useful for focusing but you can get by without it. I think it's also true that the newer high resolution LCD screens on the later cameras make live view even more effective, since you can judge focus more precisely.
  13. I've got the same JJC shutter release but I haven't had the problem you describe with my 1000D. I have had a different problem where there was a break in the cable and it only worked intermittently, but maybe you've already tried wiggling it around I ended up taking it apart and replacing the whole cable by sacrificing an extension lead that came with a hahnel shutter release, so now my JJC takes hahnel adapters for different camera systems.
  14. Alright then, here are the results of some more testing. First up we have a similar part of the sky taken with the flattener III and the improvised pieces of drink stirring stick introducing an extra ~1mm between the flattener and the sensor. I think the focus was slightly better this time (the stars are less tangentially elongated) but the flattener still gives me its classic "swimming manta ray" shape. Next up we have a different part of the sky with no flattener, so a longer focal length (since the flattener also reduces by 0.8). This is the bottom left corner and in general there is a "warp speed" effect around the edges. Some edges look weird too with stars elongated in different directions quite near each other. I checked the centre stars to make sure it wasn't trailing and they were OK. Focus wasn't brilliant through high cloud last night, so not the best test. So my conclusions for now are With the flattener is easily better than without the flattener. I haven't been missing anything. The corner star shape is very sensitive to focus. Changing the distance to the sensor by 1mm didn't make any difference. There is little scope for adjusting it further. I can try the Skywatcher flattener that Acme uses. I will lose the 0.8 reduction, but I think that will be OK. Thanks for listening.
  15. I'm pretty sure I found that page the last time I tried to fix this... I just tried measuring from the sensor plane mark on the camera forward by 56mm... it's hard to tell precisely but it looks bang on to me. Anyway, there is nothing for me to adjust. Is there a standard depth for T-adapters or is it just down to luck? I'm going to try with some bits of wooden drink stirrer between the flattener and the T-adapter. This will increase the distance by about 1mm. If that makes it worse then I'll try the Skywatcher flattener.
  16. Thanks Acme, that gives me some confidence that another combination will work. It sounds like we have very similar setups Maybe I'll order one of those... do you think they'll take the old one in part exchange?
  17. I thought someone might suggest that... the flattener attaches to the camera adapter with a T thread, so I could put something between to stop it screwing together so much... that would increase the distance a little. I can't see a way to decrease the distance. It could be clear tonight, so maybe I'll give it a try.
  18. Hi all, I have a William Optics megrez 72 that I use with my astrotrac for imaging (with a CLS filter). It's my first scope and at the same time I bought the William Optics flattener III since that was the one recommended for the scope (on the William Optics web site). However, I am becoming disenchanted with it because the best stars I can get in the corners (of an APS-C sized sensor) are like this What can I do to improve the situation? As I focus the shape of the stars changes, but they are never round. One obvious thing I can try is not using the flattener... never actually tried that but I guess it would be worse. Does anyone know of a better flattener? Maybe this Skywatcher one? The scope is 430mm and f6. Reducers/Flatteners - Skywatcher Field Flattener Will it be better or the same? Maybe that's just the way things are at this price level... Any suggesstions greatly appreciated... Mark
  19. OK, here are some test shots taken at various focal lengths. These are all 300x200 pixel crops from near the bottom left of the frame, starting with the problematic 12mm and increasing. The first 3 are f/4 and the last two are f/4.5. All are 1 minute at ISO1600. 12mm f/4.0 14mm f/4.0 17mm f/4.0 20mm f/4.5 22mm f/4.5 So, the good news is that the situation improves as focal length increases. You can choose a level of compromise and use a focal length to match. The bad news is that with the CLS filter you can't use the widest settings of the lens, so what might have been a 10mm ultrawide shot becomes a 20mm quite wide shot. I wish someone with a Tokina 11-16 could do the same tests... I wonder how well it works with the filter in place? Anyway, now I know what to do... bring on the moonless milky way! I can always try a collage...
  20. Yes, that's right. You have to turn it off before the exposure starts. You still get a little review when the exposure finishes.
  21. Thanks for replying... I'm still waiting to do tests with the same lens at longer focal lengths to see what happens... really kicking myself for not doing it that night. I'm certain that the rear element is not touching the filter at 12mm because I can go back to 10mm (where it might be touching). My theory is that the closer the element is the more of an angle the light hits the filter at... maybe refraction? Anyway, definitely agree with Phoenix that the filter is indispensable with any other lens
  22. I looked through some for the first time last night (not mine, but I'm thinking about it) and I noticed the coloured fringing too, so I guess it's normal. On the plus side I found them comfortable to use and not as heavy as I expected. The image was so big (compared to 10x50s) and the field was not as narrow as I had feared. I think I need another go the next clear night...
  23. Hi everyone, My Astronomik CLS clip filter has really improved my images taken in the suburban soup where I live, but it can only be used with EF lenses on the camera. My widest EF lens is 35mm, which is wide enough for a largish constellation but not for a Milky Way extravaganza. I have the 10-22mm zoom lens but it can't normally be used with the filter because it is an EF-S lens. However, you can remove the stopper from the back and then you can manage to mount the lens with the filter in place. I tried this last night with the lens at 12mm (to make sure the rear element wasn't touching the filter). The first two pictures show centre and bottom left from a 60s exposure at f3.5. As you can see, the stars in the corners are quite elongated. The other corners are the same, all radially stretched (so it's not a tracking error or vibration). I tried stopping down to f5, but that didn't help. I also tried shorter exposures and the stars had the same shape (so not tracking related). Here is what I got after removing the filter... the usual sorts of aberrations but much better star shape. So, should I conclude that the CLS clip filter can't be used with wide angle lenses in general? Or is it because the rear element of this lens is so close to the filter that this happens? I think my next test should be at a longer focal length (say 20mm) and see if I get more of a usable field. Has anyone else tried this sort of thing? Are there any wide lenses (10-15mm) that work well with the clip filter? I'm reluctant to spend £500 just to try...
  24. Hopefully this isn't a silly question... Are the encoders there just to allow the manual slewing feature, or does the mount use them to correct its own tracking error as well? I'm wondering how good the tracking accuracy is at those (long, to me) focal lengths.
  25. I'm pleased with mine too. I use a DSLR and the william optics flattener III. To be honest, I've never tried it without the flattener. WIth the flattener the stars in the corners take on a funny "cross" shape which varies with focus. Acme, which skywatcher flattener do you have? Is it good across the whole field (of an APSC DSLR)? For astrophotagraphy I had to tighten up the focuser a little, otherwise things can slip as you point the scope upwards. Sometimes I use a 2" 2x barlow (without the flattener) and that gets me great shots of the whole moon.
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