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Hi John
I am sure that the Meade 127mm f7.5 apo scope would be a beauty since I am very happy with my Meade 80mm f6 apo.
You are in a position when starting off to get it mostly right in the first instance. I see you are at Kinglake West which I think is about 80k from Melbourne so I guess you have a pretty dark site compared with my Sydney suburbs location. However, to do decent imaging you will need to plan for guiding if not at the start then in the medium future.
I started with a Meade 80mm f8 apo with 2in focuser which is very good for wide field use. I have this alongside a 200mm f8 Ritchey Chretien which is an excellent imaging scope.
My present range of scope focal lengths is therefore 480 and 1600mm
and I intend to get a focal reducer for the RC to give me another choice
of about 1000mm. With this range of focal lengths I can image a good range of objects with satisfactory display sizes. Also this dual scope arrangement allows me to use either scope for imaging or guiding.
Incidentally, I use a QHY5 camera for guiding (good cheap camera for guiding). You may consider starting with you DSI2 for imaging bright objects without guiding and then perhaps upgrade to say a modified
DSLR when the DSI2 will make an excellent guiding camera.
The 127mm f7.5 would have a focal length of 952mm and of course you could focal reduce to say 500mm. However, what do you intend to use for your guiding in future? In the short term however, this scope would give excellent performance with an unguided DSI2.
As far as mounts are concerned get a good one from the start otherwise
you may need to upgrade in future. Also estimate what you present and
future total loading on the mount may be and get a mount that at least
meets this but preferably with some margin over the manufacturer's maximum loading recommendations. I don't know much about mounts but
I choose the HEQ5Pro because I wanted a go-to mount, suitable for imaging use and capable of taking my total loading of 12.5Kg. The HEQ5Pros is supposed to have a max rating of 14Kg and works fine with
the above load although I did need to add an extra weight to the two provided with the scope.
Why go to? Well it certainly makes it easy to align and star find. The go-to paddle also has the facility of patching a provided cord from my astro computer into the back of the paddle (I think that most go-tos would provide this - but need to check). This permits me to control the scope from my computer star program and this greatly facilitates getting (particularly dim) objects onto my imaging camera screen. This can be quite difficult to do without a go-to and preferably program control particularly with the small DSI2 chip (a lot easier with the large DSLR chip of course). Incidentally, I use the PHD free guiding program which I regard as excellent.
Maybe you already know this but your mount will track stars in RA and in DEC when you have polar aligned. Small imperfections in the mount mechanics (such as period error of the worm/wheel) may not give sufficient stability for taking images longer than say 30sec or so.
Hence you need to also guide the scope using a separate guide scope and camera for taking long images. Even when you guide, after a long imaging session (eg I often take at least 16x6min images on dim objects such as mag9 galaxies) you may find that the separate images although fine regarding pinpoint stars may show some movement between stars on successive images over a long period due to things such as scope flexure
which guiding may not be able to overcome). Hence, when you stack the images you first have to align them. But, as I have explained, the DSI2 can subtract dark frames, align, stack images and provide a combined composite on the fly. So, it provides the facility to mark a star in the first test image to permit the DSI2 to also automatically align successive images. If you are processing off line you need to subtract dark frames from your images, align and combine them to give you your composite image. This image should have good star shapes
and a good signal to noise ratio in view of the stacking, which will allow you to adjust in a program such as Photoshop to provide a good low noise
final image presentation. For best effect you may also need to adjust composite images provided automatically by the DSI2.
In summary, think what you may want to do in the future, plan what equipment you may need and get good quality gear from the start. This way you will not be left with a lot of unsuitable gear as you proceed on your upwards journey.
Hope all this clarifies the situation.
Cheers Peter
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