questions about collimating and covers

[ApOpLeXiA]

Hello i am novice and wonder if noobies like me could also do collimating, how often would you have to do this on a Skywatch Skyliner 250-300p flextube?,

and i've seen pictures of people their flextube and they had a cover around the extension part, where is that used for and how much would it cost?, are the standard supplied occulairs good enough for Deep space objects? and would a 2*/3* barlow lens work with such a telescope?

to achieve 300/450 times magnification, and for what can this magnification be used? also to watch Galaxies?

:iamwithstupid:but very interested and eager to learn more:P

[kniclander]

on the flextube I'd guesss collimate every time you set it up

the cover is to stop stray light hitting the mirror - guess the cost is probably about 5 times what it's worth (this is astronomy after all)

the skywatcher supplied 25 mm e/p is ok but not great;the 10mm is pants

for mag divide focal length of scope by focal length of eyepiece

for dso's the general rule is low mag because they are very faint and higher power tends to make them fainter. for moon and planets 350-400 will be too high most nights of the year and can be tricky with a dob because the object will cross the file dof view in about 20 seconds. usually once you go above about 150x you won't get too much more detail except on really good nights.

hth

[rowan46]

hi collimation is something you need to do regularly, especially with a flexitube. Here is a link to collimation, it really isn't that difficult it just needs a little patience and practice.

Astro Babys Guide to Collimation

The cover round the extension is called a light shroud its used to cut out any stray light coming in from the sides and reducing contrast and helps with any dew on the primary heres the link

Dew Prevention - Astrozap light shroud for Skywatcher FlexTube

and as for your question on magnification, high powers will only be used on planets and doubles but 300x to 400x seems high to aspire to on a regular basis. I don't know how the dutch nights are but in england the atmosphere rarely lets us see much of any quality above 150x- 250x

[ItIsOnlyMe]

Hi

I was out last night with a 300p flex using a 5mm which was giving 300* mag and this was good for Saturn. I find I can use this ep on a regular basis, which is good news as it's the only good one I have :-) I live in a relatively dark village and tend to only take this scope out when the conditions are good.

As I had no power to the scope last night I was nudging as required, and as Kniclander said objects do indeed cross the field of view pretty quickly, 20 to 30 seconds at this magnification is about right.

I have tried to push the mag up with barlow / Baader fine tuning rings and find that above 300 it all just becomes difficult. Difficult to get good focus, difficult to track, but most of all difficult to find anything, guess this is because as the mag goes up the actual fov gets narrower and narrower. At 300 mag I believe you are only seeing 0.22 degrees (is my working correct here afov/mag=tfov?), take that up to 400 and your down to 0.17 degrees, IMHO the dobsonian mount just isn't up to maintaining this kind of accuracy.

[ApOpLeXiA]

aha, thanks for that information.

it does look a bit difficult that collimation:P, the problem however is my budget is not that big , 500-1000 euros or so.., so i was drawn towards a dob because it looked like you get alot of performence for a decent amount of money....

Are there any other telescopes that you guys would suggest for me (maybe ones without needing collimation), i do already have a small refractor(meade etx80)

I'm mostly interested in deep sky objects and wonder if the view threw the scope is anything like some of the amazing pictures people posted on this forum !

Advise on a telescope would be much appreciated since there are SO many to choose from!, even in the price range i am looking for.....

thanks in advance (again)

[kniclander]

def go for a dob but a solid tube won't need collimating so often, won't need a light shroud and is actually lighter than a flex tube. only benefit of a flex tube is really if you are short on space or want to travel around with it a lot and have a small car or want it to look like r2d2... .

[ApOpLeXiA]

Yes the previous model( the white one solid tube) also looks nice

but it has not the optional auto function? ( so no tracking which might be akward sometimes, also if i'd wanted to make some pictures in the future tracking is probably needed:P)

is alot cheaper tho!

300P flextube 939 euros (1195 for auto and a stunning 1795 euros for goto)

300p 779 euros

quite a big price difference, do they have the same optics? or does the flextube outperform the 300p by alot?(iow is the only difference the compacter size when stored)

skywatcher explorer 250pds also looked great (539 euros) but with tripod it is a 1695!, they only offer neq6pro system

other then that the max for a combination of reflector/refractor

would be clestron nex 6e @ 1195 euros ( this also stretches budget) and compared to a dob the diameter is quite small (half)

Skywatcher startravel 150 also looked nice (789 euros with eq5 triopod)

I am sooo lost and cannot decide at all

Please help me even more narrowing it down!!!

[ItIsOnlyMe]

want it to look like r2d2... .

That's why i got mine.

Oh, and the fact that it's not five foot long and fits in the boot of the car without folding the seats down:-)

[John]

For deep sky objects you definately want a newtonaian / dobsonian because you will get the most aperture for your £ / Euro with those by far.

The solid tube dobsonians have the same optics as the flextube dobsonains so they perform the same.

A 10" on an equatorial mount is a big scope to handle but a 10" dobsonian is relatively easy and compact when stored upright. 10" would be a good compromise I think.

If you go for a GOTO mount much of your money goes into the mount when you want it to go on the optics, in my opinion.

[ApOpLeXiA]

oke thank you! , and about collimating the solid tube, how often would you need to do that?, and can completely inexperienced people like me do it or would you need to go to someone, i have read the guide suggested here, and it didn't look that easy....

[kniclander]

my 10" solid tube only needs collimating rarely. it shouldnt need too much unless you bang it about. Also, it's the secondary that can be tricky and that shouldn't move at all once it's in place. The primary is very easy to do. problem is, you get tempted to have a little tweak here and there....

[Sarah]

I personally think collimation is daunting at first, until you have actually collimated the scope then it is much easier once you know what you are doing.

Several forum members recommend the Hotech laser collimator. Whilst it is a bit expensive, after seeing it in action at a star party and how easy it was, we bought one too. Found this video on YouTube showing how to collimate a scope using the Hotech:

We also added Bobs Knobs to the 300mm dob to save collimating the Skywatcher secondary mirror with an allen key: SkyWatcher Dob

[ApOpLeXiA]

my 10" solid tube only needs collimating rarely. it shouldnt need too much unless you bang it about. Also, it's the secondary that can be tricky and that shouldn't move at all once it's in place. The primary is very easy to do. problem is, you get tempted to have a little tweak here and there....

shouldnt move at all once it's in place???, you mean that you actually have to intall the mirrors yourself that would be sucky!

[Moonshane]

I collimate both my scopes every single time I use them (at least the primary anyway - the secondary rarely moves much). It takes about 30 seconds once you get the hang of it.

I'd forget photography for now. You will not get the wonderful images you see of galaxies etc with a dob nor with less than £1000+ (at the very least) to spend.

You can use dobs to some extent for lunar / planetary photography but just enjoy the view for now. visually, even with a decent aperture, most galaxies are faint grey smudges. think about how far away they are and they will amaze you still.

aperture is generally better for faint stuff and maybe an 8" to 10" dobsonian would be a good choice.

tracking is good but not essential. I can track manually at 300x+ on the moon with no major problems.

[kniclander]

shouldnt move at all once it's in place???, you mean that you actually have to intall the mirrors yourself that would be sucky!

oops, no i didnt mean that. the scope comes with the secondary in place - you only have to move if if it's not in the right position:)

but i think with the 300p you have to fit the primary yourself ?

honestly, dont worry about collimation - I got the hang of it and I'm rubbish at anything practical

[ApOpLeXiA]

okie thanks:P , got a lil afraid;)

[umadog]

Collimation is not difficult and shouldn't put you off buying a Newtonian. It's true that solid tubes need collimation less often, but don't let that put you off buying a collapsible if that's what's right for you. The regularity with which you need to collimate isn't very relevant because the procedure is fast and you'll need to learn it regardless of how often you need to do it.

[ApOpLeXiA]

so then the flextube might actually be the better buy since i would get better at it faster when needing to do it more often

pfff all the different choices!

[umadog]

Exactly!

With any mass-produced scope, I'd recommend checking the centre-spot position. Mine was off by several mm and views were noticeably better after I re-positioned it. I asked around and this seems to be a common tale.

[Moonshane]

Collimation is not difficult and shouldn't put you off buying a Newtonian. It's true that solid tubes need collimation less often, but don't let that put you off buying a collapsible if that's what's right for you. The regularity with which you need to collimate isn't very relevant because the procedure is fast and you'll need to learn it regardless of how often you need to do it.

this is very true and doing it more often makes it easier as far as I am concerned as 1) you don't forget all you have learned and 2) it means it generally only needs a small tweak. last time I collimated my 12" dob I literally looked down my Cheshire moved one of the collimation knobs about a 20th of a turn in the right direction and that was that (all in the dark).