'scope choice and accessories.

[bluechucky (Charles)]

Hi All,

I've been wanting to purchase a telescope for the family for some time (see http://www.iceinspace.com.au/forum/s...ad.php?t=84119) but I've held back primarily with analysis paralysis.

Fortunately finances are a lot better since that 2011 post above, and that has opened up options for me to consider.

Taking the well worn comment that no scope can be all things to all people, I've looked at what I want from my first scope. These include:

1. Not too small that it limits my viewing options.
2. Not too large that I'll struggle setting it up (I have a dodgy back) or can't lug it around with my family when we go on holidays (limited space with three kids)
3. I'd like to get a decent start into astrophotography.
4. I'd like goto and tracking to make life a little easier for the kids (and myself) in finding objects and keeping them in the view finder.

With that in mind, I've settled on the Celestron c6-sgt. I understand that it is discontinued but I think its a good scope and mount for the price (esp at Andrews communication).

So, what are your thoughts on this choice? Other alternatives I should consider?

In addition to the 'scope, what accessories should I consider?

I'll most probably get the Power Tank, and possibly the Neximage 5.

I'm stuck on the eyepieces and filters though. Not sure what I should look at getting and would dearly love to hear your thoughts on this. I was considering the Celestron eyepiece and filter set (1.25") but I'm not too certain that they are of decent quality.

What about a collimator? Bobs knobs? Dew Shield?

Thanks in advance.

[Camelopardalis (Dunk)]

My opinion is that unless you have a decently dark sky to regularly observe from, 8" or more of aperture is where it starts getting interesting!

I use an 8" SCT on both an equatorial and alt-az mount and have been really happy with what it's shown me since I've been in Australia... there's no doubt a bigger scope will show you more but they get big and heavy really quickly beyond 8". From memory the heaviest component (for the 6" or 8" SGT) is the mount itself at about 7kg...then you've got the tripod, counterweight and OTA.

I should say that for visual you will get better value from a Dob, but with the equatorial mount you can at least change the scope to suit your target. SCTs are not wide field instruments, so depending on your choice of targets for AP, you might also want a small refractor (but that's just my opinion, there are plenty of real experts in here that could give you better answers!)

[mental4astro (Alexander)]

Hi Charles,

"Analysis paralysis"! I like that one

I'll add my thoughts to Dunk's on a C8.

My first decent scope was a Celestron C5. An excellent instrument. I regret having sold it. Only thing I would say is a 6" scope would run out of puff quickly for deep sky viewing in urban areas. It will still perform very well, but light pollution will stimi the contrast. My C5 was all I needed for the moon and planets from my home, but a C8 became available & I swapped them.

Go bush with a C6, & you've got a kick arse scope. It is highly portable & light weight. Photography with a C6 is very much possible. Though with a family, I would suggest video astronomy over more conventional imaging methods. It gives a liveimage on a screen, and shows details much, much fainter than our eyes can see. As an example, my video scope is a modest little 114mm reflector. With my GSTAR camera I can see the Grus quartet of galaxies that are now invisible to my eyes in my 8" scope where I live here in Sydney. More on video a little later.

I think though that a C6 is limited to only 1.25" eyepieces. This means that the scope will give a narrower true field of view than is possible than if 2" eyepieces were used. As an exsmple, the longest focal length eyepiece that gives a 68º apparent field of view in the 1.25" format is 24mm. In a C6 it will give 62X magnification & a true field of view (TFOV) of 1.1º. The 2" format, this 68º eyepiece comes in at 42mm. In a C8 (a C8 can make use of 2" eyepieces), a 42mm gives 47X magnification & a TFOV of nearly 1.5º.

I mention all this as I'm wanting to give you tangible examples as to why consider a C8 over a C6. It is a little larger than a C6, but its footprint is just about the same.

A C8 photographically is also a more capable instrument. Though Schmidt Cassegrain Telescopes (SCT) inherently have a narrow FOV due to their long focal lengths & a slow f/ratio, this can be overcome by using a focal reducer.

Astrophotography is a complex skill. To get the results that blow our socks off here in IIS takes a lot of time & money. If you've got a family, I'd suggest video as your option. You may find that video is all you may need. To see what video astronomy is capable of doing, have a look at the work of Australia' s own Ken James:

http://www.cloudynights.com/ubbthrea...v=#Post6057527

My passion in astronomy is visual, & l have several scopes for this. Video astronomy I only employ at star parties in the big smoke. It does all I want, & that it's "plug'n'play" for me is even better. It is a shame that video isn't exploited more as I think it is probably the tool that a heck of a lot of amatuer sstronomers would actually find modt useful for imaging purposes.

Something to consider.

Mental.

[Sylvain (Jon)]

Originally Posted by mental4astro

My first decent scope was a Celestron C5. An excellent instrument. I regret having sold it.

Well, Alex, if it makes you feel any better, you can rest assured I have been taking good care of it

[astro_nutt]

Hi Charles.
Would you consider the Bintel 200mm F4 reflector on the EQ5 HE go to mount?

[bluechucky (Charles)]

Thanks for the idea's and thoughts thus far.

astro_mutt, I hadn't really thought about it but will look into it a little more.

I have read that the F4 suffers from coma issues and that the F5 would be a better choice. Is this a fair call?

I can't find details of the size or weight of the bintel Newtonian but it'll surely be larger than the C6.

Dunk, I've mostly considered C6 due to size and weight. The C8 I have discovered is not much more heavy or larger, just $500 more. I'm just trying to understand if that extra $500 would be well spent.

Thanks for your input Alexander.

Just a couple of questions. You mentioned that the C8 can take 2" EP, but I can't seem to confirm this on any of the sites, including Celstrons own site. It seems that both the C6 and C8 both use 1.25" EP. I'm a little confused there so will need to chase that up.

The video camera is an intriguing idea, and one I'm seriously considering as it seems that it'll expand the viewing options in my light effected back yard.

I'm still confused about EP's.

Is the Celestron bundle any good ( http://www.celestron.com/astronomy/c...t-1-25-in.html ) or should I invest elsewhere, and if so, what EP's and filters should I consider?

thanks again

[dannat (Daniel)]

I wouldn't get the celestron eyepiece bundle, IMO overpriced for what you get. Either start with the eyepieces that come with it, or buy some GSO plossl/superview. See what eyepieces f/l you like, then you can upgrade.
If you want to buy some reasonable ep's off the bat the BST explorer line is good value, has good eye relief & are mid priced about 75 a piece. Telescopesandastronomy astronomy in SA sell them.

Do you want goto when you buy a scope? You often pay a hefty price for goto capability.

[mental4astro (Alexander)]

Hi Charles,

The C8 is issued with a standard 1.25" diagonal & adapter that fits onto the rear of the scope (called a visual back). This adapter is removed & a 2" adapter is installed allowing for a 2" diagonal to be used. This goes for all Meade & Celestron SCTs. While the 5" & 6" SCTs can take a 2" diagonal, hole in the back of the scope isn't large enough yo allow for the best use of 2" eyepieces.

AVOID these packaged eyepieces. Not only are they way overpriced, the EPs are not worth the trouble of "upgrading". There are much bettter quality eyepieces that can be had forexperiencedmoney. I know of three eyepieces, along with a 2" diagonal that can be had for pretty much the same cost as that kit, & their quality is significantly better.

Coma is a function of fast Newtonians. The faster the Newtonian, the more coma will be visible along the edge of thr field of view. This is also more significant at low power. But, there are contraptions called coma correctors that fix this. This, for me, is only really importfor photography. I don't really find coma all that significant, even in my 8" f/4 dob that I love for the expansive wide fields I can get with it. But this is a personal preference.

So, yes, coma is more prominent in an f/4 scope than an f/5 instrument. But, don't tie your knickers in a knot over it. It can be dealt with. More important is finding a scope that best suits you.

I suggest you get to a star party or astro club to see these scopes in the flesh & in action.

Mental.

[Camelopardalis (Dunk)]

Originally Posted by bluechucky

Dunk, I've mostly considered C6 due to size and weight. The C8 I have discovered is not much more heavy or larger, just $500 more. I'm just trying to understand if that extra $500 would be well spent.

That's a difficult question, only you can really answer that I bought mine used and before I came to Australia, so saved significantly on the (inflated IMO) local prices. The light collecting of the C8 is 85% or more than the C6, so if faint fuzzies are your thing then it's a slam dunk beyond 8" the scopes become much bigger and heavier, regardless of scope design unless you pay $$$ for a custom lightweight version. An 8" scope is a sweet spot from a practicality perspective, at least that's my opinion.

You can use 2" with these SCTs but it's an additional investment. The scopes (at least the C6 and C8) have a 2" SCT thread and in the box you'd find a 2" to 1.25" visual back/adapter, and a 1.25" diagonal. To use 2" eyepieces you'd need a new 2" visual back (sometimes called SCT adapter, here) and then a 2" diagonal. Alternatively, there are SCT diagonals where the nosepiece has been replaced with the SCT thread but on an equatorial mount the ota/diagonal orientation changes depending on where it's looking and I find the unscrewing precarious...I use a Baader Clicklock 2" visual back instead (like this one) with a 2" diagonal, but Televue also do a shorter one.

An alternative to using 2" eyepieces is to use the Celestron reducer/corrector which shortens the focal length of the scope (and widens the view) and the supplied adapter and diagonal screw directly onto it.

On the subject of eyepieces, Explore Scientific do a nice range of 68 and 82 degree eyepieces that are good quality for a little over $100(US). I'd steer clear of the kit too because there's likely to be several of the eyepieces that you won't practically use, so IMO money is better spent on fewer carefully chosen ones.

[barx1963 (Malcolm)]

Good advice from Dunk and Alex re the kits, these only contain a range of plossls and some coloured filters. With Plossls usually ony the 25 and 15 are really easy to use and the filters are only really useful if you are a dedicated planetary observer. For DSO's, you want OIII or UHC type filters (if you wasnt filters at all!). In eyepieces a couple of good quality EPs will cover most needs.
Coma is, as Alex said, not really a big issue for visual use. I have an 8" f4 and the coma is noticeable but not in the centre of the field where you are looking. On the 8" f5, 12" f5 I used to use and the 20" f5 I never even noticed it. Save your money and only worry about correctors if you really feel it is an issue once you have a scope.
As far as a choice between f4 and f5 some factors that should be considered are overall cost, size and portability.
An f4 gives wider views and is a shorter scope but will be more expensive (all things being equal). As I mentioned I have an 8" f4 dob but it specilfically designed as a very portable unit so the shorter focal length was a must.
An f5 will give narrower fields, longer tube or struts and lower cost.

Hope this all helps

Malcolm

[bluechucky (Charles)]

Thanks again guys. The info has been useful. Now to make a final decision!