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IDAS ODW Clear Optical Distance Filter
The IDAS ODW is a clear filter. IDAS designed it to compensate for the optical distance when another filter, such as an IDAS NB2-PM or NB3-PM, is swapped out for the ODW. It comes in six formats with 2.0mm or 1.1mm substrates, and the DZ drop-in version has a 47mm effective aperture for ZWO filter drawers.
The "Optical Distance Worker": Maintaining Parfocal Focus with 2.0mm and 1.1mm Substrates
The "ODW" in the name stands for Optical Distance Worker. When you insert any filter into a light path, its glass substrate slightly shifts the focal point. To keep your system parfocal—meaning all filters come to focus at the same point—your empty or "clear" filter slot must contain a piece of glass with the same optical thickness as your imaging filters. The ODW is that piece of glass.
By swapping an IDAS NB2-PM or other narrowband filter with an ODW filter, you compensate for the change in optical distance. The substrate is 2.0mm in most formats and 1.1mm in the DS format.
Six Formats for Six Distinct Imaging Systems
The ODW comes in six formats. Drop-in adapters and filter drawers are sold separately.
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2" (M48) and M52 Mounted: Standard threaded cells with a 2.0mm substrate, designed for filter wheels and drawers that accept 2" or 52mm filters.
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DS Drop-in: A 1.1mm substrate filter for the IDAS AD42-DS drop-in mount adapter.
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Di2 Drop-in: A 2.0mm substrate filter designed exclusively for the IDAS AD19.4 drop-in adapter for the Celestron RASA 8 astrograph.
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DRT Drop-in: A 2.0mm substrate filter in a frame compatible with the Canon EF-EOS R, Meike MK-EFTR-C / MK-EFTE-C, and Kolari EF-EOS R drop-in filter mount adapters.
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DZ Drop-in: A 2.0mm substrate filter in a frame made for ZWO FD-M54-II and FD-M42-II filter drawers, as well as ZWO's Canon EF and Nikon F lens adapters that incorporate a filter drawer.
DZ Format Advantage: A 47mm Aperture for Full-Frame Sensors
For imagers using full-frame cameras with ZWO's M54 or M42 filter drawers, the DZ drop-in format offers a significant advantage. The IDAS DZ frame has an effective aperture of 47mm. This is larger than the clear aperture of standard M48 threaded filters, reducing the chance of vignetting (darkening in the corners) on large, full-frame sensors.
Care and Cleaning for IDAS Interference Filters
IDAS recommends this cleaning procedure.
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Step 1: Dust Removal: Always begin by using an air blower to remove any dry, gritty particles from the filter surface.
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Step 2: Stubborn Stains: If stains remain, use a lens cleaning paper lightly impregnated with a neutral (non-acidic, non-alkaline) lens cleaning fluid. Wipe gently and slowly.
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Step 3: Silicone Cloth: Alternatively, after blowing off dust, you can gently wipe the surface with a clean, silicone-impregnated lens cleaning cloth.
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What is the main purpose of the IDAS ODW Clear Filter?
The IDAS ODW (Optical Distance Worker) is a clear filter used to maintain parfocal performance in an imaging system. IDAS designed it to compensate for the optical distance when another filter, such as an IDAS NB2-PM or NB3-PM, is swapped out for the ODW.
Do I need the IDAS ODW filter if I only use one filter at a time?
If you only ever place one filter in your imaging train and do not use a filter wheel or drawer, the ODW is not necessary. Its purpose is to fill an empty slot in a multi-filter setup (like a filter wheel) to ensure focus remains constant when cycling between your imaging filters and a clear channel.
I have a ZWO FD-M54-II filter drawer and a full-frame camera. Which IDAS ODW format should I choose?
You should choose the DZ drop-in format. It is designed specifically for the ZWO FD-M54-II and FD-M42-II filter drawers. The DZ format features a large 47mm effective aperture, which helps prevent vignetting on full-frame sensors.
How do I use the IDAS ODW Di2 filter with my Celestron RASA 8?
The Di2 drop-in filter is designed to be used with the IDAS AD19.4 adapter (sold separately), which connects M42-threaded cameras to the RASA 8. The Di2 filter simply slides into the slot on the AD19.4 adapter.
Are the required drop-in adapters or filter drawers included with the IDAS ODW filter?
No. The IDAS ODW filter is sold as a standalone filter in the format you select. You must purchase the corresponding adapter (e.g., IDAS AD42-DS, Canon EF-EOS R adapter) or filter drawer (e.g., ZWO FD-M54-II) separately.
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| Brand |
IDAS (ICAS Enterprises, Japan) |
| Filter Type |
Clear / Parfocal Spacer (Optical Distance Worker) |
| 2" (M48) Format |
2" (M48x0.75) threaded cell, 2.0mm substrate |
| M52 Format |
M52x0.75 threaded cell, 2.0mm substrate |
| DS Drop-in Format |
For IDAS AD42-DS drop-in adapter, 1.1mm substrate |
| Di2 Drop-in Format |
For IDAS AD19.4 drop-in adapter for RASA 8, 2.0mm substrate |
| DRT Drop-in Format |
For Canon EF-EOS R, Meike, and Kolari drop-in adapters, 2.0mm substrate |
| DZ Drop-in Format |
For ZWO FD-M54-II / FD-M42-II drawers & ZWO lens adapters, 47mm effective aperture, 2.0mm substrate |
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IDAS ODW Clear Optical Distance Filter
× 1 (format chosen at checkout)
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Contact us for warranty details.
