Long Perng 90 APO incoming!

[Ags]

[Louis D]

17 hours ago, F15Rules said:

Are Astro Tech just a reseller, or a marketing arm of a company like Long Perng?

Astro-Tech is Astronomics's (in Norman, OK, USA and CN's sponsor) house brand, just like StelllaLyra/StellaMira are FLO's house brands.  The actual manufacturers tend to be GSO, Long Perng, Sharpstar, KUO, etc.

Synta seems to be coalescing their business around their house brand Sky-Watcher and their purchased brand Celestron rather than continue selling through Western house brands.  JOC is doing the same with their Explore Scientific and Bresser brands.  You'll still see some of their stuff under other brands, but it is becoming rarer each year.

I don't know what Sunny Ningbo is doing brand-wise since they lost custody of the Meade brand to Orion USA.

[Louis D]

17 hours ago, grjsk said:

Looking forward to read your notes on the new scope. I have a 72mm doublet myself, and I am contemplating a slight upgrade. The obvious choice would be a 80mm f7 (fpl53), but a 90mm triplet has also crossed my mind. A 90mm ED would be a perfect option (if it performs): bigger than the 80 doublet, but lighter and cheaper than the triplet.

I had been looking for a 120/125mm FPL-53 doublet when a TS-Optics 90mm FPL-53 triplet showed up used for a decent price.  I realized it would be much more manageable in size, so I went for it and have been very happy with my decision.  The only downside is that it can take 30 minutes to equilibrate if its more the a few degrees cooler or warmer outside than in my house where I store it.

Edited October 21, 2022 by Louis D

[grjsk]

22 minutes ago, Louis D said:

I had been looking for a 120/125mm FPL-53 doublet when a TS-Optics 90mm FPL-53 triplet showed up used for a decent price.  I realized it would be much more manageable in size, so I went for it and have been very happy with my decision.  The only downside is that it can take 30 minutes to equilibrate if its more the a few degrees cooler or warmer outside than in my house where I store it.

It can be a 40 °C difference where I live, but I store my gear in an outside shed, so hopefully that would not be a big problem. Do you ever have any problems with dropping temperatures while you are out observing? How big must the swing be before it becomes a problem? A 90mm ED would be a lot cheaper though, so I am cheering for the Long Perng to perform well!

[ONIKKINEN]

Scopes wont really reach equilibrium if the temperature difference is that large, not without active cooling with fans taking place anyway. Even open tube ones like newtonians have a rough time adjusting to 40 degree changes and the optics will probably remain a bit warmer than ambient through the night.

My cheaper version of this scope can take about an hour to adjust to the 20 degree difference there currently is, and at this point the lens has dewed up. So not actually sure if equilibrium is reached without some dew control.

[Louis D]

3 hours ago, grjsk said:

How big must the swing be before it becomes a problem?

Well, I definitely recall seeing it when I took it out of my air conditioned house at about 76° F into the 98° F evening, so about 22° F or about a 12° C difference.  Bright stars were spikes.  At first I thought it was pinched optics until it warmed up after about 30 minutes.  Stars were nice pinpoints after that.

I've not dealt with rapidly dropping temps while observing here.  The seeing is usually terrible under those conditions, so I don't bother.

[Ags]

Clear skies tonight!

[Ags]

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.

Edited October 21, 2022 by Ags

[Ags]

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.

[Ratlet]

I wonder if I can convince the wife to get me one for Christmas.

I look forward to hearing how you get on with dso's.  I love my 130pds but it is a bit wobbly on my az5, especially for planetary and doubles.  It's also doing double duty for imaging so for some nights I'm basically sat in a shed watching YouTube.  That is not what I signed up for!

[ONIKKINEN]

16 minutes ago, Ratlet said:

I wonder if I can convince the wife to get me one for Christmas.

I look forward to hearing how you get on with dso's.  I love my 130pds but it is a bit wobbly on my az5, especially for planetary and doubles.  It's also doing double duty for imaging so for some nights I'm basically sat in a shed watching YouTube.  That is not what I signed up for!

The AZ5, at least with a steel tripod, is an excellent match with this scope. I am not bothered at all by the wobbles that last for maybe a second after touching the slow-mo controls. @Ags if your current mount is not up to the task, i highly recommend the AZ5 with a steel tripod to match with the scope.

[Ags]

1 hour ago, Ratlet said:

look forward to hearing how you get on with dso's.  I love my 130pds but it is a bit wobbly on my az5, especially for planetary and doubles

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.

[grjsk]

8 hours ago, Ags said:

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.

Very promising indeed! The moon, planets and double stars and perhaps a few open clusters will be my only targets, so suddenly this might be a better option than a 80mm f7 or 90mm f6 triplet!

Edited October 22, 2022 by grjsk

[Ags]

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

[Ags]

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.

[badhex]

On 21/10/2022 at 12:40, Ags said:

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.

Looks absolutely fantastic, @Ags! You reckon it will be easily transportable for your trips abroad? 

[Ags]

52 minutes ago, badhex said:

Looks absolutely fantastic, @Ags! You reckon it will be easily transportable for your trips abroad? 

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.

[grjsk]

44 minutes ago, Ags said:

 I can also try the AZ-GTi instead of the AZT6.

Looking forward to your thoughts om how the AZ-GTI handles it.

[Ags]

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. 

[grjsk]

Sounds like a performer. What kind of eyepieces did you use? Prism or mirror diagonal? How was the outer edges of the views?

[grjsk]

Found this review:

https://www.levenhuk.com/reviews/ra_r90_ed_doublet_ota_review/

 

What is your thoughts on the parts about loss of contrast due to CA and SA and view at higher magnification (100x +)?

[Ags]

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.

Edited October 23, 2022 by Ags

[badhex]

15 hours ago, Ags said:

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 🤣

Weird how that happens isn't it? 😂

[Ags]

On 23/10/2022 at 06:15, grjsk said:

Sounds like a performer. What kind of eyepieces did you use? Prism or mirror diagonal? How was the outer edges of the views?

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.

Edited October 30, 2022 by Ags

[PeterC65]

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.