LtE in CMO #276

From Kunihiko OKANO

●・・・・・・・Date: Sat, 02 Aug 2003 00:40:32 +0900

From: Kunihiko OKANO <>

To: Christophe Pellier <>


Subject: Re: Mars and filters


Dear Christophe Pellier


Thank you for your mail. Your images of Mars are superb.


 The sensitivity of CCD in the range of 400nm-450nm is very important to take images of clouds. If the sensitivity of CCD in this range is low, the effect of tilting may be insignificant. As you pointed out, the tilting of filters also results in the shift of IR leak band, therefore the IR blocker is always required, even if the B filter itself has IR block function.


 My latest idea is to use a plastic filter with an interference B filter. I am planning to use FUJI-film's Tri-Acetate filter SP-4 with the SBIG or IDAS B filter. Unfortunately, I did not test this idea yet because Tokyo is still in the rainy season.


 I attached the charts of band pass of SP-4 and SP-6. The transparency by SP-4 + interference B filter will attain 80% at the peak. The SP-4 may be the best for ST-7ME (high sensitivity in 400nm-450nm range), but the SP-6 will be recommended if the sensitivity in 400nm-450nm range is low, like my ST-5C camera.


 The FUJI's filters are widely available in Japan, but I don't know the availability in France. If you could test this idea, I would like to send you pieces (30mmx30mm) of SP-4 and 6 via air-mail. I am sure that the condition of sky of your observatory is much better than Tokyo.



Kunihiko OKANO


○・・・・・・・・・Date: Tue, 05 Aug 2003 21:58:09 +0900

From: Kunihiko OKANO <>

To: Christophe Pellier <>


Subject: Re: Mars and filters


Christophe Pellier wrote:


> Dear Kunihiko Okano, many thanks for your answer! Sorry for the delay in my

> answer, I was a bit away those days.

> I'm interested to test your idea. The thing I don't understand is why you're

> thinking about using those Fuji filter in conjunction with a B interference

> filter, the transmission curves of the SP4 and SP6 look already quite good ?


This is because the SP-4 has a second passband in the range of 580nm-700nm, that is, the SP-4 is Magenta filter. Transparency of any Blue plastic filters is usually low (<50%). This is the reason why I use the SP-4 + interference blue.



Kunihiko OKANO


○・・・・・・・・・Date: Wed, 06 Aug 2003 01:39:44 +0900

Subject: ST-7MEの火星です




 B光ですが、やはり、青感度の高いST-7MEの場合には、IDAS-B+フジSP-4 が最良のはずだと思います。その組み合わせで撮りました。参考までに、SBIGBの場合も撮ってあります。東京の透明度は悪すぎて、青はあまり差が出ないようですが、とにかく表面模様はまったく写りませんので、透明度が上がってくれば多少はマシかと。




 とりあえず、RRGBも作って見ましたが、こんなもんでいかがなもんでしょうか。大したシーングでないわりにはよく分解しています。Planet Masterはやはり威力あります。シーングの良いときに、また撮って見ます。忙しくて、連続的観測というわけには行かないのですが・・・。


○・・・・・・・・・Date: Wed, 06 Aug 2003 22:28:37 +0900

Subject: Re: ST-7MEでの火星です




○・・・・・・・・・Date: Sat, 09 Aug 2003 02:00:10 +0900

Subject: 87日夜の火星です



 今度は、透明度が良かったので青にはそれなりに霞が写りました。やはり青は透明度が重要ですね。この点、東京はつらい。 さすがにRRGB合成では消えてしまうので、今回は、RGB合成です。Gの画像は30%赤を混ぜて調整しましたので、カラー画像は、あくまでおまけと思ってください。(Bは、IDAS-III-B+Fuji SP-4 で撮っています。)




岡野 邦彦 (Kunihiko OKANO 東京 Tokyo)



 Back to the LtE Home Page

 Jump to the LtE Archives


Back to the CMO Home Page