Two Mistakes

[mikemarotta]

"If you think that education is expensive, try ignorance."

In numismatics, we say, "Buy the book before you buy the coin."

I actually had the book - Harrington's Star Ware - but had not gotten to the part about the 40mm ocular ("eyepiece") before mine was on its way. 

Quote

"Also, avoid any 1.25-inch 40mm Plössl. Although magnification is very low, their apparent fields of view are narrowed than 32-mm Plössls with 1.25-inch barrels. In the end, the real fields of view (or how much sky actually squeezes into view) are actually the same, but the slightly higher magnification of the 32-mm Plössl will produce better image contrast." -- page 183. (Recommended under Getting Started on SGL under "Essential Reading" page 11.)

Mine arrived on Wednesday this week and I went out that night with my 102-mm f/6.47 refractor. The 40-mm was perfect for the Pleiades. Almost nothing else went well and surely not better than any other arrangement I already have. I will say that I used the 40-mm on eta Cassiopeiae and knowning what I was looking for and what I was look at, even at 16.5X magnification, I could see the companion. It is amazing at what you can see with just a little optical advantage. My basic intention was to use the 40-mm with a 2X Barlow to deliver the same magnification as a 20-mm but with a wider field of view and better eye relief. It just depends on what you are looking for and looking at. Just for one thing, naked eye where I live the Milky Way now is not visible naked eye. However, lining up Albireo in the Swan (Northern Cross), I saw that the Milky Way does come through with the telescope. So, it is not a total loss, and the cost of the 40-mm ocular was $20-$25, a small tuition.

On the other hand, I bought a 5X Focal Extender. The customer service rep at Explore Scientific did talk me out of it when I bought my 102 in October. He warned me that with my backyard sky and the 102-mm refractor, all I would get was a close-up view of a bad view of Mars. I bought the 5X Focal Extender a month later. I used it once and then used it again last night. It is pretty much $279 worth of nice glass sitting in a box. I do have other telescopes, including a 10-inch Schmidt-Cassegrain on loan from my local club. And our club does have a Covid-compliant dark sky site. But it was a purchase that I did not need to make.

[John]

I expect many of us have got similar experiences Michael. Things that "seemed a good idea at the time"

Many years ago I was in an astro dealers showroom and had the choice of a 32mm plossl or a 40mm. Went for the 40mm not realising that the true field visible with the 32mm would be practically the same.

The 40mm plossl does have it's uses in slow scopes like mak-cassegrains I believe. I didn't have one of those though.

We "live and learn" as they say

 

 

 

Edited December 11, 2020 by John

[banjaxed]

The man who never made a mistake has not been born.

[Moonshed]

3 hours ago, banjaxed said:

The man who never made a mistake has not been born.

Or if he has been born he doesn’t realise how many mistakes he has made and remains ignorant.

Edited December 11, 2020 by Moonshed

[Mr Spock]

I've got a 40mm lying in a cupboard. I think we've all bought one at some stage. It's a really nice original orange text Celestron.

[LukeSkywatcher]

4 minutes ago, Mr Spock said:

I've got a 40mm lying in a cupboard. I think we've all bought one at some stage. It's a really nice original orange text Celestron.

I bought the same EP from someone on SGL. It was so bad I sold it on again a couple of days later.

[vlaiv]

4 hours ago, mikemarotta said:

On the other hand, I bought a 5X Focal Extender.

That one might not be total waste

If you ever get into Solar Ha observing and you happen to get Daystar Solar Quark combo, you'll be able to turn your small F/6 refractor into very decent F/30 solar Ha telescope.

[Alien 13]

I love my 40mm, would have a 80mm if I could find one..

Alan

[vlaiv]

3 minutes ago, Alien 13 said:

I love my 40mm, would have a 80mm if I could find one..

Alan

Here is 60mm

https://www.firstlightoptics.com/specialist/masuyama-ultra-premium-japanese-eyepieces.html

and I think I saw 80mm somewhere - it is 3" eyepiece and you'll need suitable focuser and diagonal (also 3" ones).

[John]

I was referring to 40mm in the 1.25 inch fitting.

40mm (and sometimes longer) in a 2 inch or larger fitting can be spectacular eyepieces.

 

[Peter Drew]

1. It's easy enough to make long focus Plossl eyepieces with binocular objectives, if you have a lathe or Blue Peter badge.  I've made several 60mm - 100mm Plossls, they give very flat colour free images but suffer the usual problem of small apparent field and long eye relief.      🙂  

[John]

I bought one of these 32mm Erfles once, believing the magazine advert that they would deliver a 60 degree AFoV !

Of course they are limited to around 50 degrees by the 1.25 inch barrel. In fact the one that I had showed a slightly smaller AFoV than the 32mm plossl that I already had and it was not quite as well corrected

Another blooper was a 55mm ex-military plossl in the 1.25 inch format. No field stop in that one but still like looking down a drinking straw of course. 

Edited December 11, 2020 by John

[mikemarotta]

On 11/12/2020 at 13:31, Alien 13 said:

I love my 40mm, would have a 80mm if I could find one..

Alan

Yes, actually, I received similar comments on a different board (The Star Searchers). I am not dismayed. The glass is good. It just does not meet my needs and I do have other instruments that it might be a better match for.  So, thanks.

 

[Alien 13]

On 11/12/2020 at 20:05, Peter Drew said:

1. It's easy enough to make long focus Plossl eyepieces with binocular objectives, if you have a lathe or Blue Peter badge.  I've made several 60mm - 100mm Plossls, they give very flat colour free images but suffer the usual problem of small apparent field and long eye relief.      🙂  

Camera lenses (reversed) make good eyepieces but you might need 4-6 inch focusers and you should see the size of the correct image prisms if you want to use a 200mm fl one (have tried)..

Alan