miguel87

Thanks chaps. I have never bought any extra mounting parts so it must have come with two options. Unless of course rother valley optics very kindly gave me an upgrade without telling me. ✌

Ok thanks, maybe it came with two different size options of something. 👍

Advice please, Been having a proper clear out of the loft. Found a box of astronomy bits and sorting it out. What is this and do I need it? It must be from my eq5 mount. Thanks! ✌

Very nice 👍

You are proving my point here; yes the airy disc is smaller in a faster scope precisely because the image created at the focal plane is on a smaller scale (less mag). So we have evidence here that the size of the best focussed star image in a telescope gets bigger with magnification. Why else would the airy disc be bigger on longer f/ratios? If it behaved like a point source f/ratio would not affect it's image.

It is always an extended object, just a small one. As soon as the primary has focussed the star at the focal plane it has become a non point source. Due to the airy disc, diffraction of light and any aberrations present. The image of the star on the focal plane is not a point source. Not at any magnification. The book I have linked states that a point source is not physically realizable. https://books.google.co.uk/books?id=8P4gBQAAQBAJ&pg=PA74&lpg=PA74&dq=a+star+is+not+a+true+point+source&source=bl&ots=CZj7YUxKkF&sig=ACfU3U1CbyTW-qgS33AQTjSEyACGEcYUQw&hl=en&sa=X&ved=2ahUKEwil2LP-67fpAhX2TxUIHSvTC9AQ6AEwAHoECAEQAQ#v=onepage&q=a star is not a true point source&f=false Yes, it is a small object so even doubling its radius by doubling magnification will move it from about 0.7 arc seconds to 1.4. So still tiny. But the dimming process as with any other objects is still taking place. The light source remains the same so it has to dim, there is no way around that unless you argue that... 1.) it is indeed a true point source at the focal plane. Or 2.) It does not increase in size with magnification. (Which is impossible unless the focal plane image contains a point source)

Venus is covered in cloud so remains a beautiful white blob even under higher magnification. I guess I would normally view it around 100-150 magnification but depends on alot of factors.

Vlaiv was able to give the size of the airy disc for a given aperture. This is in arc seconds (0.7 for 8inch scope if I remember), so objectively not a point source. You could do the maths of the TFOV of any eyepiece divided by the airy disc diameter to figure out it's apparent angular size in the eyepiece. You could in theory then roughly estimate its surface brightness which would decrease with greater apparent angular size.

Nope. The 6mm has less glass and is much more expensive so I doubt it. Also you dont just suddenly get to a certain magnification and boom, from a tiny dot to an airy disc. Its grows and shrinks with magnification (obviously you need high mag to see this). Either way. It is not a true point source at the focal plane. Because the mirros/lenses just arent that accurate. And the airy disc depends on the size of the aperture. So as you zoom in or out, the disc gets larger or smaller, hence dimmer or brighter.

This is all I was saying, that it will dim with magnification. I know it's not huge because they are such ti y objects. Having said that, the brightness of Vega last night in my 32mm and 6mm was very noticeably different.

Yeah I get that, obviously I'm not gonna actually change the brightness of the object. But we all agree that planets are dimmer under higher magnification, because that same amount of light is spread out. If you increase mag enough on a star then you will resolve the airy disc. It will not remain a point of light because you are not examining the star itself. You are imaging the image created at the focal plane. The image on the focal plane is a disc, it has dimensions and therefore the image of it in an eyepiece will dim as it is spread out under higher mag. If the image of the star at the focal plane was an actual physical point then fine. This would need literally perfect optics. But it isnt, not even close really.

Agreed. So anything that has its light source spread over an area will dim as that spread increases?

Capture many 30 second images (maybe an hour exposure in total I.e. 120 exposures) then stack them together with free software. Stacking is how most of the images you see have been achieved. ✌

It's just a manual eq5, same as mine. Computer programs will not work.

I would mark a spot where I put my telescope (3 tripod leg marks) to use everytime. Once you have done one fairly accurate drift align I would then mark an artificial north celestial pole on your house based on what is showing through your mount's polar scope! Sounds crazy but will be very worthwhile in the long run. ✌

If you have a slightly larger budget then I personally find the vixen SLV's are another step up in quality without breaking the bank ✌

You seem well committed so I'm sure you will get it sorted with a systematic approach. I just dont like to see astrophotographers spending hours and getting results that they're disappointed with. Dont forget to stick an eyepiece in the telescope every now and them. Take a look and chill out. There comes a point where you have to be impressed with what YOU have achieved. Comparing to other results is a downward spiral. It is very difficult to put a personal spin on AP. With normal photography you can take from a different angle, put something interesting in the foreground, alter composition etc. With telescope AP, the object is just the object, same size, same angle, no foreground, no background. That is what ultimately put me off; the idea that if I got an exceptionally good photograph and spent hours on exposures, flats, parks, bias, processing. At best, I would end up with something identical to what has already been done. Anyway, I ramble! But trying to say, enjoy the results from your setup, you are never gonna get the best photo you have ever seen of M42, M57 etc etc, it's just not possible. But, it is YOUR picture. ✌

Keep going with the visual! It's an amazing hobby. One of the best things is the lack of power needed. I see many people people with laptops, cameras, guiding scopes, battery packs and heavy power banks. All I have is one battery pack the size of a TV remote which last 3-4months just to track the sky. For the 3 star align at this time of year I would just look at the plough which is virtually overhead. The stars are bright and won't be blocked by anything. You could learn all 7 pretty quickly. ✌

Call me old fashioned (I'm 90% a visual observer) but sometimes you have to take a step back and realise that there's very little wrong with those stars (other than colour perhaps). If you are a perfectionist then I guess it is an issue. But you will get beautiful pictures with the setup just as you have it. I often see stunning images of stacked 30s frames so maybe just stay shorter. Only my opinion.

The best power option for you will depend on what you are powering. Just a mount? Or cameras, dew heaters, laptop etc. If you can tell people what you need to power I'm sure you will get some good recommendations.

If tracking is a priority go with an eq mount. They are not as difficult as everybody makes out.

I dont think the OP is mounting the 150pds. Just a camera at the moment. Also I use the 200p on just an eq5 and for visual its absolutely great. Many people use this combo with no issues. The tracking motors will do the trick for a piggyback DSLR too.

Yep around the 21st of may I'm gonna go for mercury. The only planet I havent observed with the scope. It is going to be pretty near Venus then and easier to find.

Short answer is more magnification, so either a 2x barlow or an eyepiece in the 4-6mm range perhaps. The long answer is, how much are you expecting. I have a 200mm telescope and as for seeing detail to the level of ice caps (must be talking about mars) that is a once in 4-5 years sort of detail for me. I would say that Saturn will always look small in that scope but on a good night you might be able to split the rings. Jupiter, on a good night you might catch 2 or 3 bands on the planet, the great red spot is difficult but possible. I owned a 130 reflector for a long time and found 200x magnification to be pretty much the worthwhile limit. And this could only be used on rare occasions, very often you will find that zooming out a bit and observing at 150x or 100x although smaller will be so much sharper and brighter, often with more detail. In your shoes I would get a quality eyepiece around 6mm and a decent barlow lens. You will then have 25mm, 12.5mm, 10mm, 6mm, 5mm and 3mm!