Eyepieces and Accessories

[stargazer]

Guys,

Any advice to what max mag for my 4.5" newtonian? I read the general rule is 60x per inch so should I max out (scope focal lenght is 900 mm) for planetary observation? Any good brand to recommend (for newbie) and which store?

Thx

[Gary]

60x per inch as you have mentioned is just a general rule. To fully enjoy the views of a max out eyepiece (very low focal length) for planetary observation, you need excellent sky condition which is possible but very rare in Singapore. But if you dont have max out eyepiece when you finally encounter those very rare excellent seeing and transparent skies, you will be cursing yourself why you dont have that eyepiece at the point in time. So, one possible solution is to get an eyepiece that reach your max out focal length AFTER adding a Barlow lens and always bring them both together during observation. When skies are so-so, don't add the barlow. When the seeing/transparency miraculously becomes good, just add the barlow.

If you do intend to get a barlow lens, take note not to buy eyepieces of redundant focal lengths, unless you have deep pockets. For example, don't get a 20mm, 10mm and a 2x barlow.

[stargazer]

Thanks for your advice Gary....are there any shops in SG that sell astro accessories, apart from the one at Science Centre Omni?

[cloud_cover]

Hi Stargazer,
Try www.astrobargains.com or http://staropticsscientific.com
They are both local resellers (star optics is a vixen authorized distributor)
You can also try for 2nd hand EPs or just post that you WTB (want to buy) whatever EP or focal length and someone might have a spare

[stargazer]

Hi, thanks for your advice....I will take some time to shop around first to know more about the various accessories available to speed up knowledge base... cheers

[cloud_cover]

I'm in your shoes too; My very first scope is going to come in, I have no eyepieces and am quite daunted by the variety and range of prices of EPs available.
I'm most afraid of spending lots of money on EPs that I'll hardly use when I should have been saving it for a better scope/mount/filters.
One of the more experienced guys was telling me: you can either buy cheap plossls, which are decent but you might end up with a large collection of mediocre eyepeices, or you can buy 2-3 good eyepieces of wide range, a 2x barlow and be content with the coverage they provide.
Opinions?

[orly_andico]

Plossls are good.. and I think you can use them "forever."

Buying Plossls is like buying a 50mm camera lens. In fact, you'd be surprised, the optical design of the Plossl (two face-to-face achromatic doublets) is very similar to the double Gauss design of the 50mm camera lens! my point, Plossls are optically great within their limits (50- to 40-degree field, short eye relief).

For your 4.5" Newtonian, I think Plossls will do fine. Get a 32mm for wide-field (I prefer the 32mm to the 40mm, because 40mm in a 1.25" barrel only has 40-degree AFOV, so the true field of the 40mm and 32mm are about the same). This will give you 28X at 1.85 degrees true field, which is decent (the 40mm would give you 22X at 1.77 degrees TFOV).

Then get a 10mm Plossl for planetary, this gives 90X with an eye relief of about 8mm which is bad but not too bad. A 2X barlow will give you 180X which is probably more than the 4.5" newtonian is capable of, while retaining the 8mm eye relief of the 10mm Plossl.

Incidentally, around 100X to 150X is normally the most that the atmosphere here can support, so 90X with a single eyepiece and no intervening barlow is good.

It makes no sense to buy a Nagler or even Baader Hyperion for this scope since those eyepieces cost more than the scope itself. That is, unless you plan to upgrade to a better scope and keep your old eyepieces.

IMHO, Plossls are a better choice than the cheap wide-fields, because "Plossls are forever" (apologies to de Beers) given that Plossls have excellent performance. You do have to keep in mind their limitations.

The cheap wide fields have 60-plus degree fields but the edge-of-field distortions mean the usable field is about the same as Plossls.

The only exception I'd make is the Burgess/TMB Planetary. You can get these cheap at http://www.stargazer.hk (got mine for $45 USD, plus shipping, which from HK is cheap).

In my experience, a 12mm Plossl + 2X Barlow is sharper than my 6mm Burgess/TMB, but the Burgess/TMB has huge eye relief and a huge eye lens, so more usable. Don't complete the collection though, these are entry-level planetaries and you'll probably get pissed if you spend a lot on them.

[fizzy123]

Your cheap plossl can be used fro star-party or public demos. Gary's Hyperion 24mm had a number of close shave during the mpastro public star gazing session at marine parade CC. They were serving candy floss that day and a kid candy floss came too close for comfort to his eyepiece

[cloud_cover]

They were serving candy floss that day and a kid candy floss came too close for comfort to his eyepiece

Sweet! *groan*

[Gary]

Who dares to criticise my favourite Hyperion? LOL. What Orly mentioned about "unless you plan to about upgrade to a better scope and keep your old eyepeices" is very true. Another plus point about the Hyperion is that supports both 1.25" and 2" EP. When I bought it a few weeks ago for my Mak 5", I was anticipating someday I will be using it in a 2" diagonal in my mak (with SCT adapter) or in a better scope and that day has come. But after the Punggai Pentax experience, may be tempted to get a crazy high AFOV eyepiece.

Before I bought my first semi-premium Hyperion eyepiece, I bought a set of second-hand Plossls. The main purpose is to use them to find out what focal length is suitable for my scope with the intention to sell them off later once I found out and built up my dream team set of eyepieces. But now that I am into sidewalk, may intend to keep them for public stargazing sessions even after I built my dream team EPs.

I do not have a Burgess/TMB to test yet but tried 9.7 mm + 2x Barlow on Jupiter on my C8 and the on-axis view looks sharp as Orly mentioned. But of course the FOV sucked but beggars cant be choosers. So I just let if drift across the FOV and use it as teaching point about Earth's rotational speed.

For those who are interested, I am willing to share my current set of eyepieces for your testing of your scope. My only condition is that you come to Toa Payoh and do sidewalk with me while testing it.


Meade Super Plossls Set (1.25"):
- 20 mm
- 15 mm
- 12.4 mm
- 9.7 mm
- 6.4 mm

- 24 mm Baader Hyperion (68 deg AFOV. 1.25" and 2")
- 2x Antares Barlow (1.25") on loan from Zong Yao. So you can try barlowing these eyepieces on your scope which gives the following focal lengths:

- 12 mm (Hyperion)
- 10 mm
- 7.5 mm
- 6.2 mm
- 4.85 mm
- 3.2 mm