A&M/LOMO 80/600 Vs Takahashi FS78 Vs Equinox 80ED

[willis]

State of the art, classic and bargain: A&M/LOMO 80/600 Vs Takahashi FS78 Vs Equinox 80ED
At the end of last December, I was told there is short tripod for HEQ5Pro. I was delighted by this news and asked Galaxy to reserve one set for me. This is by all mean improve the portability of HEQ5Pro. At the same time my friend Xiaoer needed to buy a new refractor which is used to couple with the LS75F. We went to Galaxy and shopped. When we arrived Galaxy, we were tempted by those scopes put messily on a table! A&M/LOMO 80/600, Tak FS78 and Pentax 75SDHF etc. Our curiosity drove us to try those scopes. Due to our background, doing experiment is kind of fun. If we can perform a star test and do some celestial observations, it would be great! However, the sky sucked almost for the whole winter, it is difficult to find clear skies for testing the scopes! So we tried an alternative, indoor test! Star test is a simple and accurate method to test and collimate telescopes. Instead of using a real star, Sirius or Vega, to perform star test, we used an artificial star. Basically it generates a spot of size 50um. When place it a several tens meters apart, the angle sustained will be smaller than the Rayleigh resolution. In our case, the spot size is 50um and the distance is 25.3m. The angle sustained is 50x10^-6/25.3 = 1.98x10^-6. Roughly all the aperture of all the tested scope is 80mm. The theoretical limit of the resolution, Rayleigh resolution, is 1.2x550x10-9/80x10^-3 = 8.25x10^-6. So the artificial star is virtually a star now! There were some advantages of using artificial star.
1. In Hong Kong, it is sadly that we cannot have bright real stars when in needed.
2. Even the telescope is the same, different nights would result in different star test result. The seeing, the turbulence of atmosphere, affects a lot.
3. Real stars are moving, but artificial star is stationary. One can perform high power magnification without caring about the tracking. Collimation is possible by using artificial star too!

The artificial star we used is not white light, but R, G & B. This is a big advantage that we can test the color correction of the scopes in three widely separated wavelengths in the visible spectrum. Well! The artificial star is very good in testing telescope. But it got a big disadvantage! It costs you for more than HK$2000! Worth it or not, you think about it!

OK! Back to our main course, the optical performance of A&M/LOMO 80/600 Vs Takahashi FS78 Vs Equinox 80ED. We used TV Everbrite diagonal and Pentax XO 2.5mm eyepiece to boost the magnifications above 200X for all scopes. All three scopes gave very good green diffraction pattern, especially the A&M/LOMO. It just standout! Its’ 2nd diffraction ring was almost invisible. This result was quite expected as all telescopes are optimized for green light. We next turned the star test to red light. The red light performance is corresponding to most DSO and Ha performance. The A&M/LOMO gave excellent diffraction pattern. Both Tak FS78 & Equinox 80ED gave very good diffraction pattern. It seems that Tak FS78 gave a bit better performance than Equinox. Finally we turned the star test to blue. A&M/LOMO gave very good diffraction ring. While both FS78 and Equinox 80ED gave good diffraction pattern. It seemed that Equinox gave a bit better performance than Tak FS78.

Summary Table:
1 means excellent & 5 means bad (Subjective 5 points scale)

Green Star Test
A&M LOMO 80/600 1+
Tak FS87 1
Equinox 80ED 1
** 1+ means excellent. Textbook like diffraction ring!!!

Red Star Test
A&M LOMO 80/600 1
Tak FS78 2
Equinox 80ED 2
** It seems that FS78 is a bit better than Equinox 80ED, but not sure. A side by side test is needed.

Blue Star Test
A&M LOMO 80/600 1
Tak FS78 2
Equinox 80ED 2
** It seems that Equinox 80ED is a bit better than FS78, but not sure. A side by side test is needed.

The use of artificial star is very convenient. The seeing is not an issue and the result is reproducible if other controllable factors, say distance and brightness, are fixed. The result is quite obvious that the A&M/LOMO is by all mean the winner. All three RGB star tests of A&M/LOMO are way ahead Tak FS78 and Equinox 80ED. It is hard to differentiate Tak FS78 & Equinox 80ED, because we didn’t set all scopes side by side and do comparison. From the very beginning, we started the test after a casual talk. So no serious preparation was done. Only one tripod was used. This means we need to swap the scopes and memorize the star test result for a particular scope and do the comparison. Unless the result is very outstanding like the case of A&M/LOMO, otherwise it wouldn't be very reliable to tell the difference. In other words, there would not be big different in Tak FS78 & Equinox 80ED. If one really wants to differentiate them, a side by side artificial star test is needed.

Apart from the optics, I like the Feather Touch focuser of the A&M/LOMO the best. I have an Equinox 80ED, mounting a heavy DSLR for high magnification would be difficult. Although the dual speed focuser of Equinox is not bad, Feather Touch is just gorgeous! Try it for imaging and you will know it. It is tough and accurate. The Tak FS78 focuser is a bit behind among these three scopes in nowadays standard. So which one I would choose? If I have money, I will go for A&M/LOMO. It is state of art. However, if you are a collector or Tak fans, go for FS78. It is a classic. If you are a pragmatic user, Equinox 80 is the one to opt! It is a real bargain. Which one you would opt? Ask yourself?

[社長]

thanks Willis for the very detailed test report

也借Willis的帖分享一點體驗及資料，

1. 這個網址講及一些利用人工星點測試望遠鏡的基礎，包括測試距離，當然，若僅是用作調光軸，則距離可以大大縮短：
http://www.telescope-optics.net/star_te ... escope.htm

2. 這個人工星點是我在08年由德國帶回來的，"made in Italy" 要二千多元，上面標明是"for profession astronomers"，我的老友APM的老闆Markus Ludes每天都用這個來測他的望遠鏡，所以我經常跟人家說那個品牌那個設計那個造工如何，是有一套客觀標準的，所以這個對我的情況來說很有用，下一正還會購置一些如大直徑的光學平面鏡等，因為看來大家都很有興趣這方面的測試，而非道聽途說的了解不同望遠鏡的性能。

3. 其實這個測試結果，或多或少在意料之內，因為上面測試到的望遠鏡，三個品牌都忠於其本身設計，造工達到很嚴謹的品質要求，但在選材、成本、設計等都預視了本的的水平如何。所以很認為Willis的結論，測試結果或許稍有高低，若純考慮光性能表現，似乎剛好在價格上反映出來，但考慮到本身的售價，收藏價值，性能等，三台鏡其實或多或少符合了不同用戶的需要。

4. 測試望遠鏡中，所用的部件要小心處理，市面上的天頂鏡，以四個品牌為最佳，分別是Astrophysics、Televue、Vernonscope、Stellarvue ，其中我選Televue中最高型號的Everbrite，因為取其結構堅固，由一塊實心鋁材CNC加工而成，對我這些經常用上手榴彈目鏡的人來說很重要，當然代價是要二千多元，但一如早前一次白鷺湖天文台小組觀星夜時驗證，一些看來正常的天頂鏡，在近200倍時已看到像差，在500倍時根本連成像都有問題，在203APO隨時推上600倍觀星的情況下，別無他選了。另外因為要減中間的光學元件以免引入像差，我儘量避免用巴羅透鏡，所以Supermonocentric 4mm目鏡也略為過長，最後用上了Pentax XO 2.5mm目鏡，以上面三台望遠鏡計，倍率都在200以上，甚至250倍，所以很合適。

5. 那台 LOMO 80/600 (或許鋁筒版本的APM 80/600)被喻為世界上最優秀的80APO折射鏡，當然名氣上沒有其大哥APM-TMB 100/800APO或130/1200APO大，但我能夠配上TMB Supermonocentric 4mm及TMB 1.8X ED Barlow推上270倍看月亮，影像仍結實而合理的對比度，的確是一台賞心悅目的輕攜小鏡，也有機會帶到濕地公園觀鳥，跟旁邊的Swarovski比較，是可看出分別的，內地有有同好用來拍鳥，也是明顯比貴一截的遠攝鏡頭優秀。這些鏡頭都提供LOMO的測試報告，Strehl Ratio都在95%以上。不幸的是，這款望遠鏡已停產了。

所謂三人行必有我師，那次測試及交流過程中，我的確獲益不少。

[funoooo]

Very nice report.

It seems A&M/LOMO 80/600 is the best one.
What's the price? Is it very terrible also for new one?
Anyway, I will pay attention on this scope.
Thanks

[willis]

Very nice report.

It seems A&M/LOMO 80/600 is the best one.
What's the price? Is it very terrible also for new one?
Anyway, I will pay attention on this scope.
Thanks

For new A&M, the price is scary! The price listed is in Euro.
http://www.opticstar.com/Run/Astronomy/ ... _10_1_2_30
Act fast & share with me after u buy it.

[dormitory]

很有意义的测试 教学贴似的 收藏了

[社長]

很有意义的测试 教学贴似的 收藏了

Willis是現職物理教師，本身是研究生，所以寫這些測試報告很稱職的

[willis]

很有意义的测试 教学贴似的 收藏了

Willis是現職物理教師，本身是研究生，所以寫這些測試報告很稱職的

I am not a research student any more. I got my MPhil for more than 10 yrs! I am an old man, old cake now....

[Nebulas]

很有意义的测试 教学贴似的 收藏了

Willis是現職物理教師，本身是研究生，所以寫這些測試報告很稱職的

今天看这个帖子，我身边很多想进 80 apo 的朋友应该会有很好的参考价值。

上次在丽江认识的一个社长的女校友也是物理毕业，还和我聊到 杨振林捐赠的科学论文手稿给母校的事情。

[popkrab]

Hello,

My name is Pornchai POP from Bangkok, Thailand. I'm not too far from all of you. I like your test review very much. It is very useful and scientific tested but not too difficult to interpret them. I would like to say thank you so much for your time consume in your test review in many scopes I read. Especially LOMO APM 80/480 with several flattener, reducer.

I will try to read the forum often and will participated my test review if I can. In here I'm a member of The Thai Astronomical Society (TAS) and have a website thaiastro.nectec.or.th . Unfortunately, it is Thai.

Can you let me know your email? My email is pop@piesoft.net

Best Regards,
Pornchai POP
pop@piesoft.net

[willis]

Hello,

My name is Pornchai POP from Bangkok, Thailand. I'm not too far from all of you. I like your test review very much. It is very useful and scientific tested but not too difficult to interpret them. I would like to say thank you so much for your time consume in your test review in many scopes I read. Especially LOMO APM 80/480 with several flattener, reducer.

I will try to read the forum often and will participated my test review if I can. In here I'm a member of The Thai Astronomical Society (TAS) and have a website thaiastro.nectec.or.th . Unfortunately, it is Thai.

Can you let me know your email? My email is pop@piesoft.net

Best Regards,
Pornchai POP
pop@piesoft.net

Thanks for ur appreciation! I've sent u an email. Pls check pop@piesoft.net.

[社長]

Hello,

My name is Pornchai POP from Bangkok, Thailand. I'm not too far from all of you. I like your test review very much. It is very useful and scientific tested but not too difficult to interpret them. I would like to say thank you so much for your time consume in your test review in many scopes I read. Especially LOMO APM 80/480 with several flattener, reducer.

I will try to read the forum often and will participated my test review if I can. In here I'm a member of The Thai Astronomical Society (TAS) and have a website thaiastro.nectec.or.th . Unfortunately, it is Thai.

Can you let me know your email? My email is pop@piesoft.net

Best Regards,
Pornchai POP
pop@piesoft.net

Dear Pornchai, welcome aboard!

thanks for your nice compliments. We know "astrograph" is not the only solution for deep sky work. A premium APO with a matching flattener performs the same, and sometimes it's easier to tune to the optimal performance.

I visited Bangkok in 2006 to conduct a training on STARLAB planetarium, to a team of volunteer educators from Merck Science Institute. Also I do have customers in Thailand keep importing telescopes from me.

http://www.astro.hk/219.html

Would you share a bit about TAS' work in Thailand? May be sometimes later we will work together on different aspects.

Best regards,
Savio Fong
Director
Galaxy Scientific Group
www.Astro.hk