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lensman57

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Everything posted by lensman57

  1. The answer is yes to point 1. Your guide scope should also be pointing more or less to same spot in the sky as your telescope since if it points to another part of the sky there will be a rotation error in the final stack. Different part of sky rotate differently to each other so best to keep guider as close to the target area as possible. A slight misalignment of the scope to the mount axis can be corrected using the 3 star align routine. A.G
  2. EQ5 is a good mount, I really enjoyed mine while I had it. It should have no problem with either the 130PDS or the ED80 with all the gear . I used to use mine with a twin scope rig. A.G
  3. Well the first step is to define what is " better ". The performance of a scope can not just be defined by its optical performance. Other factors come into it such as quality of the mechanics, the optical tube, the focuser etc. 130 PDS is certainly capable of imaging at a high level in the hands of an experienced imager who is prepared to put in quite a bit of effort sorting the scope out. It will not function out of the box to the same level of an ED let alone an Apo. In its favour is a reasonably fast F5 and a lack of colour fringing due to the way a mirror focuses the rays of different wavelengths. The bad points are the flimsy construction, a less than ideal focuser as these are made to a price, possible problem with balance due to the tube length , collimation and coma. Diffraction spikes are subject to personal taste and they are acceptable on some targets and not on the others. The ED 80 is a very popular choice as a first imaging scope, it has optics which have no right to be on such a cheap scope as it can rival some no so hot triplets. The FOV is versatile so a large range of targets are within reach using a DSLR and it functions straight out of the box. The bad points are a relatively slow F ratio and a less than ideal focuser but it is functional. I can not comment on Esprit 80 as I do not own one and have not seen many images taken with one either but from the specs it seems to be a very high quality scope in a very competitive sector of the market. None of the above scopes are suitable for planetary imaging or galaxy hunting which was the point of my question in my post. As to if a scope is better than the other or is £700.00 cost difference justified I am afraid that is not answerable. Does a Takahashi FSQ 85 at nearly £5000.00 fully loaded perform that much better than an offering from APM or Astrophysics or even the Esprit 80 is subject to an individuals choice and priority. If you want scope for life then the cost of TAK , APM , Televue and the likes is justified but for a hobby that might just be passing fancy then you have to make your own mind. A.G
  4. What is it you want to do? You seem to jump from a £160.00 scope to one costing nearly £900.00. A.G
  5. This is very evocative particularly when one knows that it is our own galaxy rising. A.G
  6. You have got yourself a fast Astrograph. This means that it has been designed with imaging in mind so it should focus with a DSLR at infinity. What exactly are you focusing on and what is the distance? The best way is to try and do a dry run at daytime on a very distant object. The combination of the Comma corrector and the DSLR will have to focus very close to end of the inward travel of the focuser and with a fast scope the depth of focus is minimal so don't go focusing at light speed. A.G
  7. This is true, I usually set the Exposure compensation to + 1/2 and sometimes to +2/3. A.G
  8. Excellent first light. To add the Ha in PI you can use the NBRGB script. I usually import the RGB and Ha data into PS after processing in PI and then split the channels of the RGB highlighting the R only and then paste Ha on to the R channel. Ha can then again be added to the final image as L but the percentage should be a lot less than 100. A star mask is also used to protect the stars and the background to prevent everything from going purple and magenta. In Pi you can also do this using pixel math if you are up to it. Regards, A.G
  9. The two most important Calibration frames you should take are the Bias and the Flats. Darks will do more damage than good if not taken correctly and this means set temp cooling that a DSLR does not have so they are best left alone. Also the newer breed of cameras from Canon and perhaps Nikon do on chip dark current manipulation which complicates the matter further ( the so called raw data is not really raw) . But for now concentrate on the Bias ( the easiest to take ) and the Flats, perhaps the most difficult as how well they work depends on 1- the imaging train must not be disturbed after finishing the Lights 2- the illumination must be absolutely even 3- The level of illumination should be between 30%~ 50% of the full well depth of the sensor. Condition 1 means that the camera and the lens should preferably not be moved before Flats are taken. For 2 a decent EL panel through a neutral diffuser is the best way of going, just set the camera to Av mode and take about 30~50 flats if you find that exposure is not correct ( check the live histogram ) you can use the exposure compensation in 1/2 stop increments to take another series and see which one works best. A Flat frame as applied to the light frames is only luminance so the colour does not come into the equation with the caveat that none of R,G,B channels should be allowed to be clipped. Bias is the easiest one to take as you just set the camera to the fastest speed possible ( theoretically the exposure should be Zero to establish the pedestal value but fastest speed is fine ) and it is best taken with lens removed and the camera off the scope but with both the viewfinder shield and the camera cap on so no stray light gets into the camera and lift the Bias value. As to how many to take , the answer is the more the better. The reason is that every calibration frame brings it's own noise into the equation by taking a lot of these you are allowing the calibration software to optimise the data before applying them to the Lights. I have taken as many as 200 Bias and over 100 Flat frames and it does make a difference. I don't bother with Darks for neither my DSLR nor my CCDs. Regards, A.G
  10. In this case I think that you would benefit from the larger pixels. Point Grey Grasshopper 3 range is worth a look at if a bit pricy. Regards, A.G
  11. Hi, This was taken last week to salvage a disastrous night that everything went wrong and in the end I had to switch to a target to the south east as the mount would not guide even for 3 minutes to the southwest. I am hoping to use this as a base for star colour once the Ha and Oiii data is collected if this weather permits. Looks like another week of clouds and rain for up here. The data is only 50 minutes of 10 minute subs stacked and processed mainly in PI and tweaked in PS and I stayed on the conservative side of processing due to the limited data. 5 x 600s subs, SW 150 PDS with SW CC, Atik 428 EXC, IDAS D1 and HEQ5. Thanks for looking and best regards, A.G
  12. ACDNR in PI and the Deep Space NR in PS is what I prefer to do as well. I also find that doing NR in the linear stage such as TGV DeNoise is a real pain in the .... and for me at least the results are not very good as it leads to a lot uneven smearing in the later stages. The Multi scale Linear Transform applied sparingly in the Linear stage and a decent dose of ACDNR after stretching gives acceptable results for me if the data is not too noisy which regrettably for me it nearly always is. A.G
  13. I would have thought that for planetary imaging the smaller pixels are preferred so that the very fine detail could be resolved unless you are imaging beyond 5 Meters of FL. A.G
  14. If you have the funds, really itching to spend it and really want a CCD , who doesn't? I would then go for an Atik one with the on guider package. It really is a good deal with the 460 sensor, contained FW and guider and it also has better cooling which helps in the summer nights. There is no such thing as a beginner CCD, whatever you get the learning curve is steep but no worse than with a modded DSLR the only obstacle usually is the cost which in your case does not apply. Just don't expect to get images like Olly's and Sara's from the day go. Matt has managed to progress very quicly though. There is a hell of a lot to learn with AP so take your time. A.G
  15. I believe that 60Da and the 6D and perhaps other high end DSLRs do on chip dark subtraction as their long exposure output are quite clean for a DSLR. If this is correct then the problem it presents the imager is whether to subtract Bias or not and then there is the question of the Flats. Although I still use DSLRs for imaging I find that I am more and more comfortable with my CCDs. A.G
  16. Thank you for posting the files. The good news is that you have M13 with a hint of the propeller showing too. You also have colour and it is correct. The bad news is really evident for itself. The vertical bands could be either a driver or USB issue or both. You also need to calibrate with good flats . Regards, A.G
  17. Very nice Chris, the nebula itself looks like a floating jelly fish amongst the cosmic dust. I have no idea why they called it the Crescent Nebula. A.G
  18. This is not bad, very good in fact. You have the central star and a hint of structure in the surrounding nebula. As for guiding I am afraid that you have a difficult task with a the long FL of your scope. I would also run an instance of the HLVG filter to get rid of any green cast in the image, it is a free download for PS users. A.G
  19. Putting an FF/FR in the imaging train does not bring more photons through the 80mm aperture of the scope from the target , the only way of speeding the imaging. You will get more photons through because the FOV is wider so if the target entirely fills the reduced field one may argue for the reduction at the expense of resolution of course but if using the FF/FR makes the target even smaller no gain is achieved besides the flat reduced field, the latter is the case in the majority of widefield DSO imaging. Regards, A.G
  20. You have 3 choices. 1- An Orion / SW Field flattener without reduction ratio @ £65.00~£70.00, this already takes a 2" filter on the nose. 2- A dedicated SW FF/FR with a reduction ration of 0.85X @ approx £150.00 and about £40.00 extra for the end nose piece to take 2" filters, and the M48 to T2 adapter. Total cost about £190.00. 3- An extension tube of 50~80mm length, about £25.00 to £30.00, to compensate for the lack of a diagonal, If you go down this route get the longer extension tube so the focuser's outward travel is minimised and this helps rigidity as SW Crayford focuser fitted to its budget range are not too hot. The third option is rather a redundant one as you would need to flatten the field at some stage so your choices are effectively down to 1and 2. BTW, an FF/FR does not make F number of the scope faster, this is a myth. What it does is reduce the Focal Length and give you a wider flat field. As the Focal ratio is defined as FL/Aperture the apparent FR is reduced otherwise there would have been no need to design mega box fast F scopes, we would just use a focal reducer of 0.5X instead. Regards, A.G
  21. These are amazing images. The star shapes unlike my images are real good too. May I ask what coma corrector you are using and what is the back focus of the CC? Regards, A.G
  22. This is a nice one Chris. You have managed to tame the Ha too which is a bonus. A.G
  23. This is very good for only one hour of data with a DSLR. The FOV is also great with the Star 71 FL. I have more or less the same FOV in one of my captures of the same target but I had to use my 200L lens to achieve it due to smaller size of the sensor. A.G
  24. That is where I got my last 3 laptops from. A little more expensive than buying privately but so far no complaints from me. The only upgrade I did to my last one was upping the memory to 16 and using a 500Gig SSD so it is up to image processing. Regards, A.G
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