Some general questions about buying an 8'' Dob (in France)

[cybernautic]

Hello everyone

I'm going to buy one of the Skyliner 8'' Dobsonians, which is about as far as my decision-making process has got. I was going to get one in the UK but there just wasn't room for it in the car along with all my other stuff so I'm having to order it from a French company.

This is the one I'm thinking of at the moment:

http://translate.googleusercontent.com/translate_c?depth=1&hl=en&prev=/search%3Fq%3Dtelescopes%2Bacheter%2Bfrance%26biw%3D1024%26bih%3D613&rurl=translate.google.co.uk&sl=fr&u=http://www.laclefdesetoiles.com/browse.php%3Fcat%3D32%26brand%3D31%26prod%3D4204&usg=ALkJrhgUgFj56V1h0YVsANV6pKVj6XWO1g

That's the easy bit. I'm really concerned about being able to collimate the scope properly but from what I've read online it's something that's easier done with the telescope in front of you rather than trying to make sense of it just from a written description (which I've found really confusing).

I) What should I order with the telescope to help with the collimation? The same company sells a Celestron collimating eyepiece:

http://translate.googleusercontent.com/translate_c?depth=1&hl=en&prev=/search%3Fq%3Dtelescopes%2Bacheter%2Bfrance%26biw%3D1024%26bih%3D613&rurl=translate.google.co.uk&sl=fr&u=http://www.laclefdesetoiles.com/browse.php%3Fcat%3D146%26brand%3D26%26prod%3D4314&usg=ALkJrhiavfdylpls-t55kiJfFNyefUqdHw

Would a laser collimator be better (I'n worried about getting the wrong thing, although I don't want to spend a fortune on something that isn't going to work well with the Skyliner Dob or that's unnecessary! This collimation thing has put me off getting a Dob for ages. I've had a 60/700 refractor for years but decided to upgrade to something significantly better, especially with the dark skies I get in rural France).

Any advice re. getting the right piece of kit for a beginner to collimate would really be appreciated.

II) I want to get a right-angle finderscope too. It's either that or a red laser finderscope. Which one would I better off getting? Should I wait until the scope arrives and then decide? I'd rather order one or the other at the same time I order the telesceope. I've got lower back problems and I'm not that keen on crouching about trying to sight up the side of the telescope.

III) I'd also like to get a 2x barlow lens. Is this a good move to supplement the two eyepieces that come with the telescope itself? Does anyone have any recommendations for a beginner's barlow lens? Or would something else be better?

Lastly, has anyone had any experience of ordering equipment in France? Any recommendations for other websites/companies would be appreciated as well. In fact any advice on this would be really welcome.

Thanks for reading!

Rich

[Moonshane]

Hi there

An 8" skywatcher dob is a great choice. it has good aperture and is not too huge either.

I'd get a Cheshire collimator (not sure if that's what the link is as I could not be bothered waiting for the translation). It has less to go wrong and you can do every single aspect of the collimation with it. Collimation is hard to get your head around at first but quickly becomes an easy 'tune' before use.

The eyepieces that come with the scope are OK for a while so I'd stick with them. The 10mm might be OK with a barlow but might be too much magnification at 240x for the quality. A barlow and a 15mm plossl might be a better solution. These can be bought quite cheaply too but I'd wait.

A red dot finder like a Telrad or Rigel Quikfinder is a better buy in my opinion than more eyepieces, initially at least. I use both a telrad and a right angle finder and it's a great combination. Really helps with finding things quickly.

Never bought in France but I presume it's about the same as the UK.

cheers

Shane

[cybernautic]

Hi there

An 8" skywatcher dob is a great choice. it has good aperture and is not too huge either.

I'd get a Cheshire collimator (not sure if that's what the link is as I could not be bothered waiting for the translation). It has less to go wrong and you can do every single aspect of the collimation with it. Collimation is hard to get your head around at first but quickly becomes an easy 'tune' before use.

The eyepieces that come with the scope are OK for a while so I'd stick with them. The 10mm might be OK with a barlow but might be too much magnification at 240x for the quality. A barlow and a 15mm plossl might be a better solution. These can be bought quite cheaply too but I'd wait.

A red dot finder like a Telrad or Rigel Quikfinder is a better buy in my opinion than more eyepieces, initially at least. I use both a telrad and a right angle finder and it's a great combination. Really helps with finding things quickly.

Never bought in France but I presume it's about the same as the UK.

cheers

Shane

Hi Shane - thanks for the reply.

Is it worth getting the right-angle finder if I get a Telrad finder as well? Would it be a good idea to stick with the finder supplied with the scope and just get the Telrad as an addition? I've never used a red dot finder before but I've read a lot about them on here and it seems some people prefer them to the regular finder scope anyway. Because I've only used a 60/700 reflector before it's all a bit of steep learning curve at the moment. Like most other people, I've got a limited budget so I want to try and make sure that the things I buy are really essential.

(Meant to say in my original post that I've ordered 'Turn Left at Orion' too!)

Rich

[AndyWB]

I have both a laser and a Cheshire collimator - which is the same as the 'collimating eyepiece' you linked to. The Cheshire is more useful, the laser gets used more. The Cheshire can do all the bits of collimation, including setting up the secondary (which the laser can't). However, the laser is good for tweaks to the primary when setting up in the dark (the secondary rarely needs touched.) I'd say, get the Cheshire for now, and you can use it in the dark too, just with a torch.

I can't say I feel comfortable with collimating from scratch, but once it's about right then normally it's only little tweaks. Then again, mine is a very small scope...

[RikM]

A Cheshire is the best tool for the money. Collimation is harder to explain than it is to actually do. It is basically: get the secondary looking round and central. Line up the doughnut with the crosshairs, line up the black dot in the centre of the doughnut. Repeat again, if one of the adjustments has put one of the earlier ones 'out' again. It gets easier each time and with smaller adjustments needed usually.

Like Shane, I use both an illuminated finder (I use a Rigel QuikFinder) plus a 9x50 RACI finderscope. I use the Rigel to get in the right area and then the optical finder to dial it in exactly. The Rigel revolutionised my observing. I was (quite literally) lost without it. Changing from the straight-through finder to the right-angle correct image version, just made it a bit more comfortable and it meant that I only needed to turn the map upside down and the star positions were the same both in the finder and the main scope.

[Moonshane]

if you are getting a Telrad - I'd recommend you do - and if your choice is either more eyepieces or a right angle corrected image finder then I'd get the finder every time. you might be able to sell your straight finder for £25-30 to mitigate the cost somewhat. I just cannot use straight finders.

these two items makes more difference to being able to find things manually than any eyepiece.

[cybernautic]

Thanks for the replies. So if get a Cheshire collimating eyepiece that will collimate the scope completely without the need to buy anything extra? Something like this:

http://www.firstlightoptics.com/other-collimation-tools/cheshire-collimating-eyepiece.html

I can really only afford to get either a right-angle finderscope or a Talrad finder! I'm tempted to stick with the straight-through one that comes with the scope, get the Talrad and then buy the right-angle finder at a later date. Hmmm, decisions decisions. I like the idea of selling on the one that comes with the scope but I'm not sure how easy it'll be to sell on.

This is the correct right-angle finderscope, right?

http://www.firstlightoptics.com/finders/skywatcher-9x50-right-angled-erecting-finderscope.html

Does having the correct orientation make using books like 'Turn Left at Orion' difficult? I'm sure that uses finderscope views that are back-to-front. Do I just turn the book upside down as RikM suggested with star maps?

The collimation bridge is one I'll have to cross when I get to it. There's no point being nervous about it before I've even ordered the scope itself. My sister was thinking of getting a Dob a year or so ago but the thought of collimating it put her off too and she ended up buying binos instead!

[cybernautic]

I was looking online and found this 8'' Dob: an Orion N 203/1200 Skyquest XT8. It's got quite a good reduction on it and it comes with a right-angle finderscope and a 10mm Sirius Plossl eyepiece:

http://www.astroshop.eu/orion-n-203-1200-skyquest-xt8-classic-dobsonian-set/p,23800

Does anyone know if this compares favourably with the Skywatcher Skyliner 200P?

[RikM]

The Orion is probably optically identical to the SkyWatcher; they are both made by the same parent company. As for the Orion set, you get a 25mm and a red dot finder with the basic telescope and then a Sirius Plossl and the RACI Finder as the extras. The RACI finder is very nice but certainly not essential. Unless you bought an extra finder mounting shoe, you would only be able to fit one or the other at a time. The Sirius Plossl is better than the 10mm kit eyepiece you get with the SkyWatcher. On balance, it seems a fair package.

I would be tempted to get the basic telescope with a Cheshire and a Telrad or Rigel for now.  Stick that on the tube next to the straight through finder and use that for a while. If you find the straight through finder uncomfortable, then save up and upgrade to a right-angle finder. Yes, the one in your link to FLO is the right one and would fit either the SkyWatcher or Orion mountings.

I am afraid I don't have TLAO so I don't know what the finder charts are like. I use Sky and Telescope Pocket Sky Atlas as my 'at the scope' starmap.

[AndyWB]

TLAO is pretty good for helping you find things. It doesn't have charts with Telrad rings on, but I found I didn't really need them. Most objects have a wide view, finder view, small scope and larger Dob view. IT's pretty well designed as a guide book.

[cybernautic]

Thanks for all of the replies. It really has been very useful! I've got some idea now what to get so I'll think it over for the next couple of days.

Rich

[cybernautic]

I've decided on the following:

Orion Skyquest XT8 Dob 8'' (with 25mm EP & Sirius Plossl 10mm EP and RACI finder scope)

Telrad Finder

Skywatcher Collimation Eyepiece

To get the same things with a Skywatcher Skyliner 200P costs me more in Euros and I've been swung in favour of the Orion by the slightly better quality of the eyepieces (although I prefer the white paint job of the Skywatcher!). Unfortunately almost everything's more expensive on the continent compared with the UK but if I don't get one now then I never will.

[RikM]

Great choice of kit Do let us know how you get on.

[cybernautic]

Great choice of kit Do let us know how you get on.

Thanks to you and everyone else for the advice. I ordered the scope, the Telrad finder and the Cheshire eyepiece this evening!

I'll let you know how I get on