andrew s

Or thermal management of a Takahashi Mewlon 180c. I am probably, going to get one of these but @JeremyS and others have pointed out some cooling down issues. So what can be done? With my home made Newtonians, adding cooling fans was a breeze, however, it would mean surgery to either the tube or rear casting of the Mewlon. One technique used at some major professional observatories is to refrigerate the whole telescope enclosure. This could be possible but I was considering a less extreme idea. That is keep the telescope in a temperature controlled box with the set point set at the predicted night time average temperature or, whenever the predicted temperature was at the time I was planning to observe. I have used an air to air peltier cooler and PID controller to temperature stabilise a spectrograph so it could be repurposed to do this. Has anyone tried this or similar? If so I would love to hear how it went or any other views on this idea even if you have not tried it. Regards Andrew

I had the first carbon tube OMC 200 new from OO to use in France but sold it on as it was not getting much use as we did not spend as much time there as originally planned. However, I was clearing out my files today and came across the receipt just a tad over £2k ! Regards Andrew

It's a difficult one this. I very much enjoy the research and planning but if when it arrives there is nothing to fettle then it ca be an anticlimax. I built up my own custom mountain bike rather than buy for that reason but could have got a similar spec cheaper fully built. I enjoy making Astronomical telescope and nstruments but it is much cheaper to buy ready made. Regards Andrew

High magnification is what you want for planets but the only way to increase the field would be to use a focal reducer but I have no experience of them with a Newtonian. .Regards Andrew

What changes is where the aperture stop is in the body of eyepieces. You have to refocus because they are in different places. Parfocal eyepieces have them at the same physical location in the eyepiece barrel. The focal plane of the telescope is fixed in a Newtonian. Regards Andrew

If you look in to the bottom of you eyepiece you should see a ring of metal that defines the edge of the field of view of the eyepiece. This assume is it a simple non zoom eyepiece. This is where the telescope focuses the light. Estimate where that is in the focuser when it is visually focused and that tell you where the ccd of the camera needs to get to. Regards Andrew

An IR cut filter may make 1mm difference to focus. If you can identify the aperture stop it will tell you where the focal plane is. Post a photo of both.set ups that might help. Regards Andrew

When you focus with a eyepiece where is it aperture stop ? It will normally be inside the focus tube. That's where the ccd needs to be for focus. If you take the eyepiece out and just add the camera you should move the focus in towards the main mirror. Regards Andrew Re read your posts maybe that's what you are doing. Got confused by the barlow.tube. tuse

Robin is a very worthy winner of the Merlin Medal. He is a genuine spectroscopy wizard. Regards Andrew

To celebrate Henrietta Swan Leavitt you could get one of these https://myasp.astrosociety.org/product/GI152/henrietta-swan-leavitt-pint-glass Cheers Andrew

I am not referring to dusk and dawn flats now but to full on night flats. I have found a reference to some "blank" areas of the sky and imaged one last night. Not ideal given the moon but with a large dither and median combine it looks like it will give a good quality low noise flat. Obviously you need lots if data so several hours exposure but I can do it on nights of intermittent cloud which are not ideal for my work on flare stars. Regards Andrew

Possibly it's something I will look into if the sky flats look problematic. In theory night sky flats shoul be ideal. The main issue, it seems, is having the time to take them but this is not an issue for me. Regards Andrew

Thanks for the idea but logistically it would be difficult in the remote ROR observatory. My trial with sky flats last night looks promising even with the near full moon. Regards Andrew

On reflection I am not sure how practical they are with a CMOS camera that does not allow for scaled flats due to the non linear amp glow. However, thanks for all the input. I am experimenting with night time sky flats. Regards Andrew

Thanks for the replies. A light panel is a possibility by I have 400mm scope so ther are expensive and as its remote in a shared observatory not that easy logistically. I am trying out other options first. Thanks again. Regards Andrew

This paper seems to show it does https://www.arxiv-vanity.com/papers/1405.5540/ To quote "Reionization heats the gas and drives it out of the shallow potential wells of low mass halos, affecting especially those below a sharp mass threshold that corresponds to a virial temperature of ∼2×104 K at zreion. The loss of baryons leads to a sharp decline in the star forming activity of early-collapsing systems, which, compounded by feedback from early star formation, empties halos of gas and leaves behind systems where a single old stellar component prevails." Regards Andrew

Simple answer is I don't know. I will look into my extensive library. I do know that real data from that era is sparse to say the least. Regards Andrew

Yes the formation of neutral hydrogen let the CMB fee but it was sometime later that stars formed and their UV re-ionized the hydrogen. Regards Andrew

Thanks Martin, what time do you start relative to sun angle? Regards Andrew

If anyone takes these would you be kind enough to share you methods and timing etc. Thanks Andrew

I thought star formation re-inonised the Universe. The formation of neutral hydrogen released the CMB photons. However, it happened at a lower temperature than the ionization temperature of hydrogen due to the long tail in the Boltzman temperature distribution. I may well be wrong so will check. Regards

Ok so a bit older and shaving? Regards Andrew PS how did you know his name was Occam?

It unknowable if it's true or not. Regards Andrew

I would check what the latest Ascom can do with the asi as it may well have changed. Regards Andrew

If you Google "Christian Buil spectroscopy" he does a comparison which should help you even though it's the older Atik Horizon. Regards Andrew