Do I need a 2 inch star diagonal

[simple_legate]

I have a Skywatcher ST102, which I bought as a travel scope because I couldn't resist the price. It is in pristine condition, but I am just wondering whether it is worth getting a 2 inch star diagonal for it?

My thinking was that the larger diagonal combined with a matching 32mm lens would make a good Richfield scope. The question is, would the views be that much better than what I have at the moment which (in addition to the ones which came with the scope) are 1.25 inch Meade series 4000 32mm and 12.4mm combined with a 2x GSO shorty Barlow.

Given that I only paid $200 for the scope, I don't really want to over capitalise, so if not the 2 inch rig, is there something else I should work towards?

Thanks,

Matthew

[Camelopardalis]

G'day Matthew - don't bother with a 2" diagonal, they're too pricey IMO and with your 32mm you can already eek out 3 degrees FOV :thumbsup:

[OzEclipse]

Do you mean the SW102? 102mm diamter, 500mm focal length?

A good 2 inch quartz diagonal will probably be optically much better than the 1.25 in diagonal you have now.

You can keep it and use it on any future refractors or folded optic reflectors - cassegrain, schmidt cassegrain or maksutov style telescopes.

A 30-32mm 80-82 deg eyepiece will give you a field of almost 5 degrees with a 6.2mm exit pupil. The matching eyepieces are a much bigger investment. There are cheap wide angle 30mm eyepieces around that are not very good quality.

At one end of the spectrum, a new Nagler V 31mm will set you back most of $1000.

Andrews used to sell a 30mm 80 degree eyepiece for $79. They no longer stock it. I've heard that these eyepieces don't perform well in short f ratio newtonians. I haven't tried mine in a short newt. I have used mine in a William Optics 70mmf6 and Skywatcher ED80 f7.5 refractors and in 8 inch cass and a 12 inch Meade Schmidt cassegrain and it works very well in all these classes of longer focal ratio instrument.

I can't recommend a current cheap 32mm wide angle eyepiece that gives reasonable performance. Perhaps someone else can chip in with a recommendation.

Go to an astro club field night and ask someone if you can try a 2 inch diagonal and wide field eyepiece before you buy.

Good luck

Joe

[Allan]

A 2" diagonal is a very useful bit of gear. Coupled with a 2" wide field eyepiece, you'll experience some great observing.

One of my favourite sessions is using my 4" refractor and 31 Nagler under really dark skies. Framing several Messier or NGC objects in the same field of view is a lot of fun.

[N1]

You could approach this by differentiating between observing and sightseeing.

For observing, 1.25" is perfectly adequate, especially if the 32mm eyepiece is of decent quality. I've yet to see compelling evidence of any widefield eyepiece showing more detail and being sharper on axis than a modern, well executed Plossl or Abbe or something derived from them. It may be though that your scope (f/5) would benefit from a more complex design, which wide fields often are. That could make the outer parts of the FOV sharper.

Whether your existing diagonal is good or not optically, you find out by simply using your scope in straight-thru mode and comparing. Who says you need a diagonal anyway? There is no optical reason to use one, it's purely ergonomics and convenience ;)

For sightseeing you arguably need wide, immersive views. I totally agree that this adds to the experience.

[bigjoe]

Yes! Get one.

A 2" diagonal , especially dielectric has transformed every scope I've used it on; more so

if you do not know the sky so well .

A big rich field is what awaits you!

Cheers bigjoe.

[simple_legate]

Thanks all for the helpful responses. I did mean the SW102, with the 500mm focal length.

I will take some time to test the telescope straight through and see how much of a difference that makes.

The other thing I notice, is that Andrews has 2 inch diagonals that range from $50 (non name brand) to $300 (WO) with GSO just on the cheaper end of the midway point. GSO seems to sell a plain bk7 diagonal, a bk7 dielectric and a quartz one. Assuming you largely get what you pay for, and given that the bk7 is half he price of the dielectric one, what is the extra money paying for (it doesn't look like much more than brand with the WO diagonals, as they are only 1/10 wave compared to th 1/12 wave GSO ones).

I realise these are often subjectiv distinctions, but it is not easy for me to get out to an Astro club to see for myself, so is there something I am missing?

Thanks again,

Matthew

[Tropo-Bob]

Matthew, enjoy the scope as it is. You actually have 2 EPs that will give decent views. U can spend a lot of money on marginal improvements. If U continue to enjoy this hobby, buy a 6" or 8" Dob. This will again be a huge leap forward in what U can observe.

[simple_legate]

Thanks Bob,

I actually had intended to buy a 10" dob until this came along, and I couldn't resist the price. I like it because it sits close to my front door and in a minute or so I can be observing. It probably gets a run 3 nights in a fortnight which, for me, is not bad. My wife thinks all I look at is the Plieades and the Orion Nebula, which is not too far from the truth, because I really like to look at things slowly. I was really happy the other day, when I discovered a new (for me) star in the Orion Nebula.

I don't mind buying extra things like eyepieces etc if I can get full value out of them, but I would not like to spend the money on marginal improvements, as you say. The star diagonal I am currently using is not the 45 degree erecting diagonal that came with the scope, but a Meade one (918A I think) that I bought while upgrading the focuser on a 60mm scope I happened across.

So while I am digesting the advice here on diagonals, should I save my pennies for a larger scope (even though I worry I won't get the use out of it I get from this one) or is there something else I really should buy first? One of the things I would like to know is what the equipment acquisition path looks like, particularly if you don't have a huge amount to spend.

Thanks all,

Matthew

[N1]

Use what you've got and do not spend big money until you understand fully what it is that you want.

[Kunama]

Agree !

and don't get too hung up on marketing specs like 1/10 or 1/12 wave with these cheaper line items, I seriously doubt there is too much testing going on with these mirrors.
I have seen some that were claimed to be 1/10th wave that would not compete well with my shaving mirror, yet others that were of the cheaper line were nearly indistinguishable from the top tier ones.

Buy used gear to save a small fortune.

[bigjoe]

Hi Buddy.

If you intend to sell the acro one day soon don't bother spending on dielectric .

Instead save some pennies for a 8/10 dob; scope of a life time, if you're not going into long astro photos.

These scopes are wide field and wil show great detail in globulars eg Tuc 47 (have a look at that), some spirals m83, the jewel box even from a city!

Cheers bigjoe.

[Tropo-Bob]

Matthew, A red dot finder will make finding things easier or conversely, if U stumble across something interesting, U can use the red dot finder to see exactly where the telescope is looking. If U buy a dob later, U can easily transfer the finder over to the new scope. I have brought ones that now sell for $39 and they are reliable and work well.

Also, a 20mm EP would probably be useful. Many rave about the GSO Superviews with their widefields that sell for about $60. Personally, I had one but sold it cheap as I did not like it. (Did I have a dud, or just too addicted to quality widefield EPs that go for a few hundred dollars each?). A 20mm Vixen Plossl goes for $65. These are very light EPs. I own Vixen 15 & 30mm EPs and like both. A 20mm EP would also be useful later, if U buy a Dob.

[simple_legate]

Thanks Bob,

I have a red dot finder, which came with the scope, but I don't know the relatively quality of this for Skywatcher products. I will take a look at the Vixen EPs, which seem like my price range. How do they rate compared to my Meade series 4000s?

Matthew

[Atmos]

Not sure how they compare to the Vixen as I've never looked through one but the Meade 4000 aren't half bad :)

[Tropo-Bob]

I have never used a Meade series 4000 EP, but they have a very good reputation. Some say the Meade Plossls were almost the equals of the original Televue Plossls. I suspect the Vixens might just be a shade inferior to the 4000s, but are still good EPs.

[Renato1]

I've got three small refractors that take a 2" diagonal. I occasionally fit it to them. But, together with a big low power eyepiece it makes them back heavy, and somewhat more awkward to set-up or to use. So I tend to use a 1.25" diagonal most of the time with a 16 to 20mm wideangle eyepiece - since what I want to see well usually requires higher power than that from a 32 to 40mm eyepiece.

I suggest that you just keep checking out the classifieds here, till something relatively inexpensive comes up.
Regards,
Renato