Astrodon

David,

Would you be willing to make a set of large Sloan filters (5" X 5" clear aperture) for a 24" Schmidt. If so, how much?

OK, I know that is too much without even seeing the price. But how about two of the five, g' and r'?

OK. How about only r'?

David, they would end up being thousands of dollars each. I can check, but is this within the budget? If so, please send a formal request for quotation to don@astrodon.com.

Sorry, I meant to say Don, not David.

Hi Don I've enjoyed reading your info on narrower narrow band filters. I have one question. Assuming equal transmission and no impediment due to fast optics, would it ever be the case that a wider narrow band filter would be desirable? For example, if you have limited exposure time with only mild light pollution, might a 3 nm OIII filter leave the background black point clipped while a 10 will give a smooth background?

Hi Bill,

Assuming no change with fast optics, the narrower OIII filter will produce higher contrast and S/N, but this depends upon keeping the same high transmission at the emission line as in the wider filter. This is our advantage in that we can make a 3nm filter with 95% transmission at 500.7 nm. Thus, you are not giving up signal in going from a 10 or 8 nm to a 3 nm narrowband. That goes direclty to the S in S/N. The narrower filter will linearly decrease your background, which is important when the moon is up. The narrower filters inproved contrast and bring out more structural detail for this reason so long as the S stays strong with high transmission. I use the same 30 min exposures for my 5 nm H-a and SII and 3 nm OIII for this reason. The exception my be H-a. The narrower 3 nm H-a filter strongly reduces the NII contribution and therefore, for certain objects you may not see an improvement in S/N due to the loss of the NII signal. Hope this clarifies. Don

Hi Don,

Which of your filter sets do you recommend using with an ATIK 314L+ camera? It uses a Sony chip and is an interline camera, but it isn't a Kodak interline chip.

Thanks,

-Jim

E-Series for the Sony ccds. Not a perfect choice but this gives you better OIII balance for doing planetaries. Your R:G:B should be 1.25:1:1.

Hi Don,

Another Atik question. Do the 1.25" E series filters fit in Atik's filter wheels? I have read that Astronomik filters will fit but some others will not because the filter mount is too deep and rubs against the cover. If you can provide the height of the mount, both the threaded and unthreaded parts, I can follow it up with Atik.

Thanks, Andrew

Andrew, I don't know. These are standard 1.25" filter holders that fit SBIG, TruTek and QSI CFWs. I think they all standardize on the screw-in thread specs. Don

Hello Don - I just received two sets of your filters (RGB and NB) with my new QSI camera and noticed what I would describe as very fine dirt particles on both filter surfaces which is visible under a strong light when the filter is held at an angle. A clean brush and air removed larger particles but the fine ones remain. Can you recommend a safe cleaning procedure or is it a non-issue?

Thanks - Jeff

Jeff, we clean and inspect every filter that leaves Astrodon. If they become dirty, here is my cleaning procedure: 1. Place a lint-free wipe (like a KimWipe) on a clean table 2. Wet it in a 2" spot with a few drops of 91% isopropyl alchohol that you can buy at Walgreens 3. Holding the filter from the sides, preferrably with finger cots, blow both sides of the filter with oil-free compressed air (just be careful not to spray on oil or water from a compressor or can) 4. Place the filter on the whetted area and using no vertical force, lightly drag it to a dry area on the wipe. 5. Remove and repeat for the other side. Don

Don - I am buying a Kodak ccd camera with the 8300 sensor with 3326 x 2504 array, and 5.4 micron pixels. Would your E series or I series filters be best for that sensor? Thanks.

E-Series, Dave.

Hi Don, I consider to order photometric filters from the UBVRcIc series for delivery to Germany. Is the price in this case the same as listed on your web-Site or are any taxes deduced (like e.g. VAT)?

Hi, Stephan, international shipping via USPS will be added to the price of the filters. You will likely have to pay your import duties or VAT to pick up your package in Germany. Don

hi don i want buy solar eclipse filter for my canon 5D camera pls give me advise iam a photojournalist in delhi india. Hi, Asif, i don't make anything specific for a solar eclipse. Sorry. Don

Hi Don, I am using your 3nm filters with a celestron 14" and Hyperstar adapter for F/1.9. I am imaging in Southern California and the filters have worked great. My questions is since I am shooting so fast would your 5nm filters give me better results.

Thanks

*****Hi, Gary. please the the Narrowband FAQ page at http://www.astrodon.com/Orphan/astrodonfaqnarrowband/ where this is discussed.

Could you provide a link to some images taken at f/2? There will be significant signal loss from the 3 nm filter at f/2 but, you're so efficient at grabbing photons at f/2 that it perhaps somewhat makes up for it. The issue is transmission loss vs. gain of perhaps 1/3 less sky noise due to light pollution at your location. I don't have much experience at f/2 as I do at f/3 with an E-180. My guess would be that you'd be better off with the 5 nm filter at f/2. Don

Thanks Don, I got the filters before I realized the difference made by fast F's. I have read your FAQ and wanted your opinion. I may have to get the 5nm filters from you but have pretty good results so far. I am using the QSI 583. I have put a 20 Minute unprocessed Ha at this site: http://www.linear-dims.com/out/Ha_20MIN.zip ****Hey, that's pretty good for f/2 wit ha 3 nm filter. Kevin Nelson at QSI indicated that there would be about 10% vignetting with our 31 mm inserts an that's about what I see in your image. I see the curtains in back of the HH, a clean Alnitak with almost no halo and a bright Flame nebula. If you stacked 5-7 of these, I think you'd get a good, high-contrast image. If you went with the 5 nm, you would add signal with increased transmission, but your bkg signal would also go up do the the wider filter, so the gain solely due to increased transmission would be partially cancelled, and the HH region and curtain are not a very strong emitting region. I think you're probably fine with what you have IMO. Don

Gary, may I use this 3nm H-a image of the HH on the site? What is your email?

Thanks Don, You are more than welcome to use the image. I post most of my images at: http://picasaweb.google.com/gary.gonnella I would be happy to send you high rez copies of any of these or just the raws if you want. The last 2 images in my ...LOOK HERE FIRST... folder were built with these images all at 10 Minutes with total exposure of about 2 hours for each filter. My confusion may be from the fact that short F's were said t cause filter shift. Being an old Ham I think of shift as moving the center frequency off of the desired point. From what I now think i understand it is not a frequency shift but a decrease on transmission. If this is the case I am thrilled with a little loss to get past my high light pollution. My email: gary.gonnella@gmail.com

********Please take a look at our Narrowband FAQ from the narrowband page. It is indeed a spectral shift of the bandpass with incident angle of light moving the peak transmission off the emission wavelength. So, instead of being on top of the curve, you're part way down the side. Don

Thanks again and I love the QSI with your filters.

Dear Sirs,

I have just purchased a set of LRGB E- Series Filters.

From Ian King here in the UK.

Could you please tell me how I can identify the anti-reflection surface, so I can face this towards the chip.

Many thanks

Kind regards

Simon

Sinmon, please see our Narrowband FAQ. The same applies to the RGB. http://www.astrodon.com/Orphan/astrodonfaqnarrowband/#h18 Don