Celestron Astromaster 70 frac EP Upgrade

[Jaywillis78]

Hi,

l recently got the above mentioned scope cheap off eBay. I just wondered if someone can tell me if it's worth getting extra EP's for it.? I would like to get a higher power one for Planets. It has no Barlow with it so what's the highest power I could go to with it, maybe a 7 or 8mm EP? Thanks in advance.....

Jay

[ronin]

I suspect the eyepieces supplied were low on performance so a half reasonable plossl should improve what you see. If I am correct the scope is 70/700 so is an f/10. Meaning a plossl should be OK and from the value of the scope it's not worth you going mad on anything else. Although that is up to you

Get a 10mm and as you have highlighted a 7mm or 8mm, for wider maybe a 25mm or 30mm.

As to possible power the 10mm will give 70x and the 7mm therefore would give 100x.

Estimate that 100x is where the quality will start to drop off, it is a case of what is your preference - slightly bigger image but a slightly less good image, this in turn is dependant on what you re looking at Saturns rings are probably best if small and sharp, whereas observing doubles not so relevant.

Really owing to cost, scope and eye relief sticking to a 7mm as the smallest to use.

Check the classifieds here and elsewhere as plossl's appear and are inexpensive.

[Jaywillis78]

Thanks ronin, so the Skywatcher SP plossls on FLO for £20 would be an improvement over the stock ones? They have a 7.5mm which sounds perfect. But they state suitable for F6 and faster scopes, whereas mine is a slow scope?

[John]

Slow scopes are kinder to eyepieces. I suspect the advice on the plossls is that they are good for scopes slower than F/6.

[LukeSkywatcher]

I'm unsure if a 70mm Celestron scope with supplied eyepieces, is really worth investing in "better" eyepieces. The scope in question has a focal length of 900mm............is that an f10 scope?

It depends on the supplied eyepieces. If they are Celestron Plossl, then they are pretty good. If they are Kellner then they are pretty rubbish.

Sure even Skywatcher Plossl's are slightly better, but is it worth investing in them?

I dont think the issue here is the EP's................its the apeture.

I say stick with the eyepieces that came with the scope unless they are Kellners. If that is the case upgrade to bog standard run of the mill Plossl's for about £30 a pop and the difference will be noticable.

[ronin]

Thanks ronin, so the Skywatcher SP plossls on FLO for £20 would be an improvement over the stock ones? They have a 7.5mm which sounds perfect. But they state suitable for F6 and faster scopes, whereas mine is a slow scope?

Not looked but that sounds like a misprint by FLO or you have read it wrong, easy ehough to do either way.

Most plossl's will be OK at about f/6 but a slower scope like your f/10 are even better for them.

If it doesn't state it then I think that it should read f/6 or slower.

TV plossl's that are supposed to be intended to work down to f/4 are £75-80+ each. In general the faster the scope the better the eyepiece needs to be and that costs.

Just checked the FLO site and it says f/6 or slower, not faster. :grin:

Will say the example in whoever's hand makes it look like a big chunk of metal, bit surprised at that, even if it is a 35mm.

I would always rather a person try a few eyepieces then buy based on what they have been able to peer through, but that means borrowing a few. These days the concern is that costs are getting cut and that usually means quality is as a consequence. I din't have any Skywatcher plossl's to comment on, and to be honest haven't used a plossl for some time. I bought the BST Explorers. Also don't have a scope bearing a similarity to yours. Do have some Celestron plossl's around that I used some years ago and they were fine, and on a faster scope then yours.

FLO do tend to pick reasonable items to sell, so that would mean they like the Skywatcher's. However it is still a case that a TV plossl will far outstrip a Skywatcher plossl, but you are talking £20 or £80.

The 7.5 should be a nice size - unless you wear glasses ???

If you wear glasses then you may not be able to get close enough to see well.

I see that Cardiff Camera Centre have it listed at £22, that looks more like the size I expected

CCCPl

From your signature I am guessing you could call in there, FLO have a £3 postage cost do the CCC one would end up £1 less.

Apologies: The search was for Cardiff Camera Centre but I see it says Newport, left it for information.

Know there is a club near you, if you are a club type person give them a visit.

I don't like saying "Yes, buy one," they may not be as good as you would expect, but a 7.5mm plossl on an f/10 scope should work well and I cannot come up with a reason not to.

Check out places like Rother Valley Optics and Sherwoods to see what they have, these light evenings mean there is not that much observing time.

[ronin]

It was me that said f/10, I assumed it was one of the numerous 70mm dia, 700mm focal length ones that are around. Several brands seem to have them with their name branded on the sides. All will come out of the same place just a different name on them. Sort of "best guess".

[Jaywillis78]

Thanks John, I get it now.

Thanks Paul, I'll have to take a look to see if there is a name on the EP's. I guess if I do get additional ep's I'll be able to use them when I can eventually get a Mak 127 GOTO. So it wouldn't be a waste on money in that respect.

thanks for the feedback both!

[Jaywillis78]

Thanks Ronin, I'll check the other suppliers out this evening. Yes I see I got my fast and slows the wrong way around, d'oh!!

Thanks again for the great reply, lots to look up and think about. Might check out the BST's as they'll be used when I upgrade the scope in the winter hopefully.

[LukeSkywatcher]

This is basically what a Kellner eyepiece looks like:

Pretty naff. So any Plossl will be an improvement.

[Jaywillis78]

Thanks Paul, my ep's look nothing like that, they are longer and have Celestron written on them both. And certainly look nicer than the one in your photo. :-)

[LukeSkywatcher]

Thanks Paul, my ep's look nothing like that, they are longer and have Celestron written on them both. And certainly look nicer than the one in your photo. :-)

So i am guessing that they are Celestron Plossl's. Not bad EP's. Keep them. No reason to upgrade.

Do they look anything like these: with rubber flip up eye guards?. If so..................they are fine and pretty good, no need to upgrade really..............unless you really want to but i dont see why youe should.

[Jaywillis78]

Yes, the left three look very similar, 20mm and 10mm are the ones I have with the scope.

[LukeSkywatcher]

Yes, the left three look very similar, 20mm and 10mm are the ones I have with the scope.

So you have a 20mm,10mm and an 8-9mm Plossl.

They are keepers.

[Jaywillis78]

Sorry no I have a 10mm, 20mm and I want to get a 8mm plossl to try an improve views of Saturn but I appreciate view conditions are not great this time of year.