Hutech IDAS LP filter - update.

[centroid]

Following on from an earlier 'thread' of mine, when I found the Hutech filter to give a distinct magenta 'cast' to my H9C OSC images, here's the latest update.

Last time, there was an unknown quantity in the equation, in that H9C was, at the time, way below spec, due to a faulty component. So, the Hutech filter's performance was given the benefit of the doubt.

The camera has since been back to SX, for repair, and now seems to be performing as it should (full dynamic range).

Despite the full Moon, a couple of nights ago, I tried on NGC2244 again (I had an image taken with the filter, when the camera was below par, for reference). The resulting image still had evidence off magenta 'cast' showing, which I corrected with colour balance adjustment. Not particularly bad, but enough to notice.

Last night, again despite the full Moon, I tried the camera/IDAS filter on M81. This resulting image, when debayered, had very distinct mauve/blue colour showing in the stars and galaxy. Trying different daybayer offsets, only produced completly nonsense results.

Debayering in alternative software, gave no improvement either. The next time I get a clear sky, I'll give M81 another go, but this time I'll replace the IDAS filter, with the IR block that I've always used.

Dave

[Psychobilly]

Show me a LP filter which is effective with a color OSC without givign some colour cast and I'll buy two please... i only get a slight Cyan cast to the satrs with mine which is very easily processed out... much less of a color cast than the Astronomik CLS-CCD which is still easily processed out... and as for the Lumicon Deep Sky......

Any chance of showing us a "Raw" unprocessed - color balance wise image Dave? I know SteveL and Steppenwolf both use the IDAS on OSC's

Billy...

[SteveL]

There is something very wrong somewhere, the IDAS LPS2 doesnt cause any of the large colour shift that you mention on any of the scopes I have used it on (Hyperstar/MakNewt/WO66/ED80/C8/C11 and with either the QHY8 or M25C).

It is the "P2" filter isnt it? What does the writing on the filters edge say?

[centroid]

Peter, I wouldn't be able to 'post' a RAW FITS image, as they are just too large for this 'board'

Steve, yep its definitely marked P2, and its the scond filter I've had, as the first one fell apart, and was replaced by SCS, so its unlikely (albeit not impossible) that both filters, are optically faulty.

The 'proof of the pudding', will be when I repeat the image with the IDAS filter removed. If the results are 'normal', then it has to be the filter. If not, then something isn't right with the camera.

Dave

[Psychobilly]

Sorry Dave what I meant to say was not played with colour wise.... a crop showing the color shift would be fine...

Heres a crop from a widefield image of M101 taken through the Megrez 72 FF III IDAS P2

Straight autosave from DSS with only the RGB black level adjusted.. that slight cyan tinge is all I normally have to deal with...

Peter

I have used the filter on the equinoxe-66, Megrez 72 and CPC 800 and with the modded and unmodded 350D and 1000D and the slight Cyan is all I have to correct..

[centroid]

Ok, here's last night's M81 image.

Ignore the 'noise' and the poor quality, as it was only 6 subs, with a very moonlit sky.

No colour balancing has been applied, its just as debayered.

Update: here's an old (Feb 08) m81 taken without the IDAS filter, albeit through the 12".

Dave

[steppenwolf]

There is something very wrong somewhere, the IDAS LPS2 doesnt cause any of the large colour shift that you mention on any of the scopes I have used it on (Hyperstar/MakNewt/WO66/ED80/C8/C11 and with either the QHY8 or M25C).

I have both the 1.25" and 2" IDAS LP Filters (P2 type) and I haven't noticed this magenta cast on images from either of my two OSCs (SXV-H9C and SXVF-M25C) so I too suspect the problem lies elsewhere.

[centroid]

As I said Steve (s), if it disappears when I repeat the excercise without the IDAS filter in-line, then it can't really be anything else but the filter.

If it doesn't disappear then further investigation will be needed.

A very remote chance I know, but its possible that SCS received a 'duff' batch of IDAS filters.

Its not related to the camera being repaired, as I noticed, and 'posted' the fact that I was seeing this colour cast, before it went for repair.

Its not the 80mm APO, because the colour results through this scope, before I had the IDAS filter, were fine. Also, although we now know that the H9C was faulty (low dynamic range) from 'day one', it had always produced clean images with no colour cast.

So, if I were Sherlock Holmes, I'd now be arresting this Hutech filter on the evidence to hand, but as it is, until I taken some images without it, I will give it the benefit of the doubt

Watch this space!!

Dave

[centroid]

Well, as I said "the proof of the pudding.....", and here's the result.

M81, taken with the same camera (H9C), and some scope (80mm APO), but this time no Hutech IDAS LP filter, just the normal IR blocker.

No stange cast anymore.

So, as I've heard said, the IDAS filter works with some peoples LP sky, but not my minimal LP sky, it would seem.

Looks like I'll selling a virtually brand new £120 filter at a good discount

Dave

[Psychobilly]

1.25 or 2"...

Billy...

[steppenwolf]

Interesting result, Dave and against the 'grain' but I certainly can't argue with your test results! How would describe your LP, high, low? To give you an idea of what I have to contend with here (and my Hutech works wonders with no colour cast), the following is a totally unfiltered 11 X 120 second Canon 300D image of M31. I am only continuing the discussion so that others can make a more informed choice over the purchase of this particular filter as, historically, I have always sung its praises from the rooftops!

[beamish]

It's a 1 1/4" Billy ,already asked .

[Psychobilly]

Oh well ...never mind.... i'll srick with the CLS for camera-2 for a while then...

My lp results would be similar - if anything a bit worse than Steves...

Wierd.... but based on the images taht you have posted Dave - undeniable... it would be interesting to see what an Astronomik CLS or Lumicon Deepsky would do on your setup...

Billy...

[centroid]

My LP is nothing like that Steve

In fact, compared to that, I'd say that my LP is really quite low.

We have no street lighting in the village, and I'm six+ miles away from the nearest town to the north, and twelve miles from the one to the south.

E, S, & W, my skies are pretty good, but the LP to the north is quite noticeable. However, I rarely image to the north, as that which is in the north at one time of the year, is E, S or W at others.

I guess it was my inquistitive nature that tempted me to try an LP filter, and the Hutech seemed generally regarded as one of the best.

However, as it didn't work for me, then £120 was an expensive way of satisfying my curiosity.

As I've heard said before, whether or not the IDAS filter is effective, is very dependant of the degree of LP at a particular location, and hence it works for some and not others.

For the mono imager, the colour cast that I saw in my OSC images, would not be a issue, and I can believe, that for some, having the filter is the difference between being able to image and not.

So, I'm not denegrating the Hutech filter, but just saying that in my case, it introduces and unwanted feature in my images.

For you, and SteveL, it has proved to be a very useful accessory to have.

"Horses for courses" I guess.

Size?, yep as Karlo said, it is a 1.25" ( I think the 2" is signifcantly more expensive than the 1.25")

Dave

[Psychobilly]

Yep and like eveything else "astro" has gone up significantly in the last few weeks

I bought one On Steve's Recommendation and its works for me... but sounds liek your skies are pretty darn good.. I have 2 streetlights within 20 feet of the obs and seeign as we are above the road they are only a few feet above our ground level

Billy...

Billy...