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.

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.

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?

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.

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.

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

I haven't noticed field curvature when using an ES68 20mm, but field curvature strongly depends on your eyesight, so don't read too much into that. All high magnification views have been with a Speers WALER 4.9 mm (102x). This eyepiece can be adjusted to work as a 3.1mm too (160x). I am using a prism diagonal. I'll compare the views to a mirror diagonal when I get better skies.

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? As far as high magnification views go, I have only been able to observe a few double stars so far, and it has performed really well. I haven't had a chance to look at the Moon, and my views of planets have been through thick haze. I will post my findings on these targets when the weather gods relent.

That's superb - I personally think M42 is hard to make good-looking, but you have definitely succeeded!

Not sure what scope this is.... Startravels are definitely not ED scopes. Do you have a picture?

Just had another brief session through rapidly thickening haze. I have attached a freebie 6x30 straight-through finder as a weight-saving experiment, and finding targets at zenith with a short tripod is rather challenging! But I did eventually find Epsilon Lyrae and quickly judged the setup is a lot more stable with the lowest section of the tripod's legs retracted. So I upped the magnification to 160x, and got a beatiful split of both components with black sky between them. The haze at least gifted me with super stable seeing. However after this it was too hazy to find any other dim targets, so I switched to the last thing still visible, namely Jupiter. Unfortuntely the big planet was in a glowing ball of haze and only the main bands could be made out. But good news - my travel setup can work with a slightly shorter tripod and some yoga on my part. And this scope is going to be a great companion for hunting doubles. I almost forgot - I had a good look at Vega looking for CA and there was a trace, but very subtle.

I find out in a couple of weeks 😀 It should fit in carry-on luggage. It's exactly the size I was told it would be, but it is much bigger than I thought it would be 🤣 Regarding stability, I am trying tonight with somewhat retracted tripod legs... I can also try the AZ-GTi instead of the AZT6.

A few small negatives... The foot on the telescope is too short for reasonable balancing, so I have attached a short dovetail using the two 1/4" thread holes in the foot. The handle makes the telescope much more manageable and they provide 2 alternate attachment points, but the handle attaches with just one screw - two screws would be far more secure. Also the scope has no instruction manual.

I would add carbon stars and planetary nebulae to that list 😀

So far I am pleased with its performance on doubles, and planetary looks promising. I get to dark skies in a couple of weeks, so I will be able to comment on DSO performance then. However, the ZS66 is an ace on DSOs at a dark site, so I have no doubt the LP90 will perform superbly in this role too.

The haze is just getting thicker but Jupiter was still visible so took a last look. The red spot was on show and nicely visible despite the misty haze. In the ZS66 the red spot is just a star-like dot, but the shape was easily observed in the LP90, so the larger scope clearly showed its resolution advantage.

Well, actually the sky is perfectly clear - inbetween the clouds... 🤣 I managed a quick look at a few random stars with a 20 mm eyepiece (25x) and felt the ergonomics of the telescope work well at low power. I went out again an hour later. Transparency is poor and Jupiter is a little dim and lacklustre - maybe later when it is a little higher will be better. I will need to rethink my mounting options as I don't think the AZT6 head and Artcise 60C tripod are up to the job - 4-second settling time after focusing at 102x. However, I didn't see any CA on Jupiter and image was sharp. Moving on to the Double Double, I got good splits of both pairs at 102x, which is clearly better than the ZS66 and C6. Albireo showed gorgeous rich colors. Zeta Lyrae and Achird were also good. Despite the faintness of Achird's companion, it was clearly red. Polaris' companion was clearly visible, so a (predictable) win over the ZS66. I had a look at the ET cluster, but its not really the night for DSOs. I haven't seen any chromatic aberration so far, although I suspect the rich star colors may be due to residual CA. I'll have a go at Mars later if the clouds permit. My impression is it is a nice instrument to use, not too heavy, easy to point and focus and a good focus snap. As a disclaimer, I have astigmatism and observe without glasses, so I am not best placed to pronounce on optical quality.

Clear skies tonight!

I've got a thread about this one, but reposting here for the record - Long Perng 90mm APO.

Old vs new... scopes always look smaller on the internet! It is a solid thing, pure neutronium. Long Perng probably make battleships and tanks on the same production line. I thought I wasn't going to attach the handle but I have changed my mind - when I figure out how to attach it. Lovely big lens 😀 It's somewhat heavier than the ZS66, but I think you get a lot more glass for the weight. The focusser feels very nice. The dew shield is nice and deep.

Here is the same animation but split into 3-minute sequences.

Apparently the scope arrives on Friday, and the internet says Saturday is clear. Testing targets: Epsilon Lyrae - expecting a clean, easy split. Albireo - expecting good, pure colors. Ring nebula - a side by side comparison with the ZS66. Mars - will the scope cope with a very red target? Double Cluster - it is always "wow" but will the LP90 be more wow than the ZS66? Pleiades - ditto. Jupiter - more color, more resolution? Any fringes? Vega - check for CA... Polaris - is the companion easily spotted, unlike the ZS66? Also: compare mirror vs prism diagonal.

Here is a short slideshow (not quite an animation) of 48 minutes of action.

The Long Perng 90 comes on Friday!