Long Perng 90 APO incoming!

[badhex]

1 hour ago, Ags said:

It's not clear to me which version of the scope is being reviewed here? As it is sold with different types of glass, we need the reviewer to be more exact.

They do say one lens uses special glass, but my version makes a song and dance about both lenses using special glass?

I am pretty sure that this is the one you have. Ernest notes the model number (44741) printed on the box - did yours have the same? Anyway sounds like a great little scope! 

http://astro-talks.ru/forum/viewtopic.php?f=7&t=1151

Edited October 23, 2022 by badhex

[Ags]

16 minutes ago, PeterC65 said:

Since there are a few different versions of this scope, could you perhaps provide a link to the one you bought? I've been following this post as I might be interested in a bigger aperture refractor but having searched for the one you have online, I'm still not clear about which model it is.

 

https://www.teleskop-express.de/shop/product_info.php/info/p11436_Long-Perng-90-mm-f-5-5-SD-Apo---Dublet-Objektiv-mit-2-Sonderglaesern-und-2--RAP-Auszug.html

[Ags]

17 minutes ago, badhex said:

I am pretty sure that this is the one you have. Ernest notes the model number (44741) printed on the box - did yours have the same? Anyway sounds like a great little scope! 

http://astro-talks.ru/forum/viewtopic.php?f=7&t=1151

The labelling on the lens cell is the same as mine. Looks like the same one.

I see two reviews have now been posted here for the scope, but one looks like a translation of the other.

As far as planetary views go, I am hoping it provides good views, but note 'good' is defined for me relative to a C6 and ZS66.

[Louis D]

The focuser has obviously changed over the last 9 years from the original flat tube to R&P connection:

The telescope is equipped with a Crayford focuser: when the focusing wheel is rotated, a relatively thin axis rotates, which is pressed against a flat groove on the movable eyepiece tube

vs.

2" RAP dual speed focuser, ball bearing and tooth drive adjustment

I have the Long Perng 72ED under the Astro-Tech branding with the flat tube focuser setup from that era.  I can attest it badly slips under heavy loads near zenith regardless of the tension settings.

[badhex]

5 hours ago, Ags said:

The labelling on the lens cell is the same as mine. Looks like the same one.

I see two reviews have now been posted here for the scope, but one looks like a translation of the other.

As far as planetary views go, I am hoping it provides good views, but note 'good' is defined for me relative to a C6 and ZS66.

Ah yes, seems like Levenhuk have simply copied Ernest's review (and possibly not credited him). Looking forward to hearing more on planetary performance, it should at least be half decent if the CA is controlled well enough - and there's always ca-reduction filters like the Baader options. Hopefully sounds like you won't need them though! 

[Ags]

The trouble is the ED version has been offered with FPL51 only, or with FPL53*. I don't see mention of Lanthanum before 2019 however, so maybe they updated the optical formula since Ernest's review in 2013? I'm intrigued, so I have asked TS to clarify.

*Although it is claimed the FLP53 versions actually used FPL51.

[Ags]

3 hours ago, badhex said:

Looking forward to hearing more on planetary performance, it should at least be half decent if the CA is controlled well enough - and there's always ca-reduction filters like the Baader options. Hopefully sounds like you won't need them though! 

Even if you are lucky enough to own a takahashi, there are nights where a simple Wratten #8 will help with atmospheric dispersion... Or have I uttered heresy?

[grjsk]

Ernest mentions the product number S500-D. Your is S500G-D. That extra «G» might indicate a change.

[ONIKKINEN]

Should also note that there exists a version with no fpl51/53 glass at all, like mine. Mine has an achromatic doublet with the other lens being lanthanum glass, so basically a semi-achromat.

So are there 3 variations of the same scope being sold?

[grjsk]

21 minutes ago, ONIKKINEN said:

Should also note that there exists a version with no fpl51/53 glass at all, like mine. Mine has an achromatic doublet with the other lens being lanthanum glass, so basically a semi-achromat.

So are there 3 variations of the same scope being sold?

I think Agnes’s scope is an updated version of Ernest’s, because I can’t find his scope for sale anywhere. Yours is S500G-C. So 2 versions for sale at the moment as far as I can tell.

[grjsk]

Nope, APM sells a white one; S500M. Crayford focuser. Unknown glass. So atleast 3 versions.

[badhex]

4 hours ago, Ags said:

Even if you are lucky enough to own a takahashi, there are nights where a simple Wratten #8 will help with atmospheric dispersion... Or have I uttered heresy?

Haha we're not on the Tak thread so I think you are safe! I must admit I have never really used any coloured filters for planetary. 

[JeremyS]

2 minutes ago, badhex said:

Haha we're not on the Tak thread so I think you are safe! I must admit I have never really used any coloured filters for planetary. 

Walls have ears 🤣

[badhex]

18 minutes ago, JeremyS said:

Walls have ears 🤣

Damn I forgot you had Google notifications for certain SGL keywords like "tak" and "handle". 

At least I didn't mention slowmos and night vision or Stu would be in here as well. 

... whoops 

[Ags]

I got a reply from the efficient support team at TS today:

"fpl51+lanthanium is a very recent news, from 2019 you are right. chinese made a big step in advance in producing high quality glasses and...they created new configurations. tthey did an excellent job in my opinion."

As Ernest's review is from 2013, we can't apply his findings with respect to higher magnifications to the current iteration of the scope. I imagine adding a lanthanum element would sharpen up the higher power views. Using the Wayback Machine, it seems until the lanthanum variant was introduced, TS never advertised the scope as a planetary performer.

I had a few minute of clear skies to the south, and had a quick view of Saturn. The scope certainly bests the C6 and ZS66 on this target - I was seeing the ring shadow on the planet very clearly for example. The view was comparable to that given by my best planetary scope so far, a 102 mm Mak (long since sold, it was my only scope for 10 years so I remember the views quite clearly). Bear in mind Saturn is rather low for me so the poorer seeing low down would of affect the bigger aperture of the C6 more.

My friend pronounced the travel tripod + AZT6 setup "rather wobbly" so it is now set up on the AZ-GTi and Berlebach tripod waiting for Jupiter to arrive.

Edited October 24, 2022 by Ags

[Ags]

I had a rather longer look at Jupiter, the AZ-GTi and wooden tripod providing a much more stable platform. I feel able to draw some firm conclusions on the planetary performance, namely that the scope is in the same ballpark as a 102 mm Mak. There were some traces of color around Jupiter, particularly if my eye was off-axis, but the contrast was very good and colors were vivid. My friend exclaimed "All the moons are different colors!" and I agree, the yellow of Io really stood out. The red spot, just creeping into Jupiter's sunset, stood out clearly with a sharply defined shape. The two main bands were well defined, and other bands came into view at times. At 160x I could make out some detail in the NPZ.

Edited October 24, 2022 by Ags

[Ags]

I'm in the UK next week... Do I or don't I ship an OVL Nirvana 4mm to my holiday address? Decisions!

[grjsk]

30 minutes ago, Ags said:

I'm in the UK next week... Do I or don't I ship an OVL Nirvana 4mm to my holiday address? Decisions!

I assume the Long Perng travels as well? If so, the answer is (obvously) yes!

[Ags]

Sometimes you've just bought too much stuff, I'll make do with the Speers WALER 4.9 mm.

It was still clear when Mars rose over the neighboring row of houses so I had a look at a very red target finally. At 160x it was still very small but the phase was clear with a hint of whitening at the north and an L shape of dark features below that.

[grjsk]

How did you manage the finderscope with the AZ-GTI? I noticed in your picture that you had the scope on the right hand side, putting the finder in a workable position. The AZ-GTI in alt-az mode puts the scope on the left side, causing the finder to be under the scope. Can either the foot or the findershoe be placed at different positions?

[Ags]

The AZ-GTI firmware is updated to right-hand mode. Don't forget the focuser rotates, so it should be possible to get it in a good position in left hand mode too.

I don't see any holes for mounting the finder on the opposite side.

Edited October 25, 2022 by Ags

[grjsk]

9 minutes ago, Ags said:

The AZ-GTI firmware is updated to right-hand mode. Don't forget the focuser rotates, so it should be possible to get it in a good position in left hand mode too.

I don't see any holes for mounting the finder on the opposite side.

Oh, the focuser can be rotated! I missed that part. That takes care of that problem.

[Ags]

This scope is really great, aside from being a bit bigger than I had hoped it is performing perfectly. I have had my doubts about the Speers WALER 4.9mm eyepiece, so last night I sensibly changed to an SLV 6 mm slightly barlowed to around  4.5 mm. With this combination at least, I didn't see any false color around Jupiter and Mars. Mars is still too small to judge, but as I watched Io drift over the surface of Jupiter I couldn't think of ever having a clearer view of the big planet.

[grjsk]

22 minutes ago, Ags said:

This scope is really great, aside from being a bit bigger than I had hoped it is performing perfectly. I have had my doubts about the Speers WALER 4.9mm eyepiece, so last night I sensibly changed to an SLV 6 mm slightly barlowed to around  4.5 mm. With this combination at least, I didn't see any false color around Jupiter and Mars. Mars is still too small to judge, but as I watched Io drift over the surface of Jupiter I couldn't think of ever having a clearer view of the big planet.

Prism or mirror?

[badhex]

52 minutes ago, Ags said:

This scope is really great, aside from being a bit bigger than I had hoped it is performing perfectly. I have had my doubts about the Speers WALER 4.9mm eyepiece, so last night I sensibly changed to an SLV 6 mm slightly barlowed to around  4.5 mm. With this combination at least, I didn't see any false color around Jupiter and Mars. Mars is still too small to judge, but as I watched Io drift over the surface of Jupiter I couldn't think of ever having a clearer view of the big planet.

Glad to hear you're enjoying your new frac. I love my ZS73 but there is definitely something to be said for the larger aperture of my TS102. No doubt you feel very similarly about the difference between your ZS66 and the Long Perng 90!