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The right OTA


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I'll post my setup as a little premise :

Meade 8" f.4/5 F=900 Newtonian

Skywatcher HEQ5 Pro

Skywatcher finderscope+ spc900nc

Modified Nikon D40

I know it sounds silly but I'm developing a hatred for my telescope. When I bought it back in January I was delighted with it as it was my first equipment piece, even though I knew I was going to wait a few more months for the mount.

Instead now that I'm testing it I'm finding all kinds of flaws, some I think rational, some due to the stressful nights it led to  :p

The first problem is the focuser is a 1.25" clunky and unbelievably long rack and pinion, far from good for photography. I thought about enlarging the hole and upgrading it to a 2" but working on the tube seems a recipe for disaster and it's possible the secondary mirror still won't be big enough to project a full image. The second thing which is making me truly paranoid is the weight. At 25lbs with finderscope and camera mounted, and just as much needed as counterweight, my constant worry is that I'm putting too much strain on the mount and shortening its life, aside from the difficulty in mounting everything. The motors look so tiny compared to the weight they have to shift ! And to add to it the mount's tripod's feet cracked and came off during the third night, which only added to the fear...It's tormenting!

I'm considering buying another but with so many options available it's trialing. For example I thought about an 80ED refractor first, but there are also 102mm and 120mm  regular achormats with a similar price and I really wouldn't know which option is better.

I know it's diffcult since there's a mix of scientifical considerations and experience (a heavy and hard to mount scope can result in less nights spent outside and less imaging too) to make but I really want to hear your opinions. With the goal of dso imaging which scope would you pair with an heq5 if you were starting over with a budget of £300-400 for the ota ? 

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Sounds like it is not as enjoyable as everyone would like.

First I will say that if you are going imaging then would you consider adding an ED 80 to the collection ? I say adding to as the newtonian is better for visual and you may as well be equiped for both.

The mount should handle the equipment at present.

Weights should not be the same as the OTA and accessories, would have said about 1/4, so 25lb bits and about 6lb weights. Not sure what the assumptions are that you have made for the weights. Perhaps more on that later.

I would leave the achro's out of it, they produce too much CA for most imaging purposes.

In a bit of a generalisation an 8" reflector is more biased to visual. It is I think mainly the physical size. As you seem to have found hauling one onto a mount is not easy they also will have a biggish area so catch any wind and ultimately they have a longer focal length.

Cannot help about the tripod foot, I am trying to remove one of mine and it is resisting the idea.

Back to an ED 80 - they are generally a little slow, f/7.5 I think, you will want a reducer flattener, Usually the diagonal is removed so you could need an extension tube. They are not as heavy but they do not float either. Not sure if they come with tube rings. You can always check the used market as ED 80's appear at reasonable intervals.

No idea where Treviso is (SW ???) are there any clubs around, they may be a source of information and advice.

The only Treviso that appears on google maps is in Italy, North of Venice.

If that is where you are then I guess that suggesting the used market may be a little irrelevant as the SGL classifieds and most of the ABSUK sellers are UK based and when private sending to Italy is a bit more involved.

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If you stick with the reflector i would go for a 150P-DS not because it's slightly bigger than the 130P-DS but it will take a Moonlite Focuser as a upgrade, I don't know if there's a upgrade path for the  130P-DS, you will also require a Coma Corrector......

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Thanks for your kind replies in particular Ronin (yes, that's the right Treviso). I actually just read the other thread where they talked nicely of the 150P-DS although I'm a bit reclutant of buying the same type of telescope of the one giving me woes, even if this one clearly has more perks.

Fortunately we do have a nice portal (astrosell.it :p ) for used gear and I just saw there are a couple of SW 80ED too, going for around £200-210. I was thinking of maybe buying a refractor and keep my newtonian aside to work on as sort of a side project.

Something else I've been wondering about is the performance of regular achromats when imaging with filters. If you shot with an h-alpha, green, and blue filters wouldn't you be able to align the images in post-processing and overcome the refractor's chromatic aberrations ?

For the counterweights I used this website http://www.robincasady.com/Astro/WeightCalc.html, I thought you want the scope to be perfectly balanced to avoid strain to the motors; at the moment with 23lbs of weights I can put the scope parallel to the ground, release all the clutches and it won't move at all. Am I doing it wrong :huh: ?

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