Skywatcher Dobs

[Tac]

I have been looking at scopes for a good few weeks now and I have yet again changed my mind on what to get. I was originally looking at a 200PDS on a NEQ6 mount as I wanted to get in the photography side of things, but then again which newbie doesn't? . Anyway I don't even have a DSLR yet and I think if I want to do this then I'll go down the Frac route.

What I've been looking at now is a large Dob for visual and save the pennies for if or when I want to start imaging. I'm currently eyeing up either the 200 or 250 Dob. Probably the solid tube version but that'll depend on the size and my storage area limits (as well as what the missus will allow ). Also not sure on the tracking or GOTO option yet either but this does add a lot of extra expense.

I do have one question though. I notice (on FLO's site) that the 250 is listed as a PX which I think means it has Pyrex Glass. Is it only the 250 that is available with this and what difference would it actually make?

Oooops, just noticed that's two questions

[gedmac]

i can answer 1 question..........the 200p is not pyrex glass:) but a very worthy scope,as large as i would like to handle in one piece moving it from storage space tp observation site.the 250px is quite a bit bigger."stole" this pic from another post:p here,s the link ~:http://stargazerslounge.com/beginners-help-advice/128173-look-size-thing.html

[Jon65]

Tac,

The way I understand it is the 250mm PX has a parabolic primary mirror made of pyrex glass.

The 200P means its a parabolic mirror,though some European outlets stock a 200PX dob.

I believe the pyrex has a faster cool down than standard plate glass or any other type of glass used in reflecting scopes.

After lots of research and head scratching I settled on the 250PX dob,hoping to take delivery of the 250mm PX dob asap ,should have been today but it did not arrive. & .

Jon

[Tac]

I'm leaning the 250PX way too. Shame yours didn't come but probably not a major issue with all this damn cloud

[Jon65]

Tac,

The 250mm PX is a good choice and an excellent price,14 years ago I had my first 250mm dob, it was second hand,fairly newish at the time and homemade, it cost £350 back then but it did perform brilliantly.

Sadly broken up and recently sold on.

I've posted some sketches as to what is possible with the 250mm in one of my SGL albums.

As long as the weather improves for galaxy hunting season come the end of March.

[Ad Astra]

You should be very happy with a 250mm dob! Wonderful size - great deep sky views, still not so darn big that you can't pick it up and move it easily by yourself.

You can also easily construct an off-aperture mask to make your 250mm f/5 into a 100mm f/12 for wonderful planetary and lunar work!

Looking forward to 1st light report and photos!!!

Dan

[Tac]

Yeah looking forward to it. Strange they dont seem to do the Pyrex in the 200 or 300.

I'm definitely gonna learn to walk before I run so a nice Dob first then if I keep up my enthuisiasm I'll move onto imaging with a Frac and still have the Dob for visual while the cameras are running.

Another quick question. I'm 6 foot 2 and was initially put off by the Dobs because of the constant bending down. How tall are they and how often are you bending. My back isn't what it used to be and that's before I've even started. Would I be better getting a Newt on an EQ mount instead?

So many possibilities and descisions to make. Arghhhh

[Tac]

You can also easily construct an off-aperture mask to make your 250mm f/5 into a 100mm f/12 for wonderful planetary and lunar work!

Interesting. Do you have any more information on this?

[Jon65]

Tac,

I expect at your height you will require a bar stool or something similar for seated views at a 250mm F5 dob,or you could raise the base,I 've done that before with the three base "legs" on bricks so I'm at a comfortable height at the eyepiece,I'm 5'10" and shrinking though with my bad back and age.

I had an off axis mask for my old dob,it was made from some thick black plastic.

The idea is to fit a cover over the end of the scope with a 4" diameter hole in it away from the centre "off axis".The idea being so all the lovely planetary light isn't obstructed by any of the spider vanes when fitted on the scope,essentially it will perform as well as any 4" refractor and very useful if seeing conditions for the full 10" aren't good.

I used velcro to peel on/off from the end of the scope,it was a really basic version of one.

Hope that made sense waffling now, and ready for bed.

Jon

[Tac]

Yeah that makes sense. Thanks for that.

[yoda]

Hi Tak I to am quite tall at 6'1'' and I have a 250PX Dob, you will get a bit of back strain but five min's away from the scope and a good strech seems to work for me.

If you do go for the 250PX you will not be disapointed, great for DSO's and not to big to carry in to the garden alltho if you are going to a dark site away from home then you may have one or two problems all the best Andy.

PS: The 250PX is about 4''6' tall when pointing to the zenith.

[dobbie]

Hi just to pick up on as astra post have you more details of a apeture mask how does it change a 250mm into a f12 planetary scope? .

Sent from my HTC Wildfire using Tapatalk

[Tac]

A quick Google solved it for me. It's basically a cover you put over the scope with a 4'' hole cut into it. It changes it to an f/12 because of the ratio of aperture to focal length i.e. 250 aperture divided by the 1200 focal length equals 4.8, rounded up to 5 (f/5). Whereas 100 aperture divided by 1200 focal length equals 12 (f/12)

You could probably use the endcap that comes with the scope for this or get a second one to modify.

[swamp thing]

Hi

When i use my 10" Dob which is f/4.5 I use a drummers stool (they are height adjustable). It puts the eyepiece at a comfortable height all the time. No back worries.

Regards Steve