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Description
This is a premium quality 2"Starguider H-Alpha filter with a 7nm bandwidth made by Optolong for Starguider.
Buy once - buy well. Just compare our numbers with others that are on sale - we doubt you will find better specifications or price.
At Sky's the Limit we test each filter individually. No between this and that figures - what you see is what you get. Each Ebay listing is individual to the filter being supplied.
It is a very narrow band filter and can be used to improve contrast, capture new details and to combat light pollution.
H-a filters work particularly well on emission nebulae, but can also be very effective in reducing the effects of light pollution and in reducing star saturation and bloat. It is for use with a CCD camera or DSLR camera - it must not be used for solar viewing.
On request you will receive by email an A4 sized colour spectrum graph with readings made with our own Avantes spectrometer. We test each filter to ensure that it meets the specification quoted. Our graph shows the peak transmission %age and at what frequency. Our spectrometer also measures the bandwidth (also known as FWHM - Full Width at Half Maximum). We also supply the data relating to the transmission at H Beta, Oxygen III and Sulphur II. Upon request we can also supply the full spectrum readings as an Excel file.
Here's the actual graph for this filter that you will also get with this purchase on request (less watermark - email download):
Performance
Starguider/Optolong filters offer performance as good as, and in some cases better than, the top brands currently on sale. We have printed here so that you can compare this to similar curves from other suppliers.
And here are the very important figures derived from the spectrometer readings:
2" Ha 7nm no.15
| Nebula's light (nm) | Transmission T% |
| H-β 478nm | 0.23% |
| H-β 479nm | 0.16% |
| H-β 480nm | 0.09% |
| H-β 486.1nm | 0.02% |
| O-Ⅲ 495.9nm | 0.11% |
| O-Ⅲ 500.7nm | 0.06% |
| H-α 656.3nm | 80.65% |
| SII - 672.4nm | 0.34% |
| Artificial light (nm) | Transmission T% |
| Hg 435.8nm | 0.35% |
| Hg 546.1nm | 0.04% |
| Hg 577.0nm | 0.01% |
| Hg 578.0nm | 0.01% |
| NA 589.6nm | -0.01% |
| Na 615.4nm | 0.03% |
| Na 616.1nm | 0.05% |
| Max Tx%= | 84.26 |
| @ nm= | 653.86 |
Peak Transmission = 84.26% @ 653.86nm
FHMW = 8.08nm
Quality
Each filter is built upon a precision polished substrate of Schott glass. The filter will retain its 'as new' optical performance for more than 10 years. It is resilient to scratches, moisture, dew, and humidity.
Price
No silly RRPs but an host price for an outstanding product.
Sky's the Limit are pioneers in bringing exceptional value items to the astronomy market. Started in 2004 we have been importing and selling optical products at prices others only wish they could achieve. By dealing directly with the manufacturers and suppliers in China and keeping our overheads low in the UK we are at the forefront of the bargain price supply chain. We aim to be the lowest prices in the UK and we aim to offer the best service that you would get from anywhere. Our integrated warehouse and distribution facility is linked directly to Paypal so that your order can be processed and dispatched without delay.
Why buy from us?
Have a look at our feedback and you will see the common theme is that we communicate well. Before a sale, during the processing of the transaction and after you have purchased an item you have access to a telephone number and email address both connected to a human being who knows what you have been sold. We will do our utmost to make things as smooth as possible for you - especially if you are new to astronomy or to Ebay, we all had to start at sometime. There is no such thing as a silly question, please ask knowing that we will treat you courteously and respectfully as we hope you will want to come back to us if you choose to upgrade or buy some extras for your hobby.
We will not leave you in the dark!
Skies Unlimited is the Ebay trading name of "Sky's the Limit". Feel free to email any questions through Ebay.
Payment
Please pay as soon as possible after the auction and we will get the items to you with minimum of delay. We usually get goods on the way within 24 hours (weekends excepted).
Paypal is the quickest way to pay. We accept Postal Orders, Bank drafts and Building Society cheques and deal with them like cash so your goods are dispatched as soon as we have the payment.
Please do not send cash through the post.
Terms of Sale
All goods, unless otherwise stated, are brand new and in first class condition.
Compliments may be made at any time.
About Us
Sky's the Limit have been trading on Ebay since 2004.
Our aim has always been to:
- Provide quality goods at the best price possible
- To treat our customers as we would only dream of being treated ourselves
We work hard to maintain a 100% satisfaction rating and in order to achieve this, should anything not be quite as you expected it to be, all we ask is that you give us a chance to put it right.
If something is faulty, we will put it right at our expense with all shipping costs refunded in full. You will not be out of pocket.
If you change your mind or ordered the wrong thing you can return it within 30 days preferably with all packaging, inner and outer, for a refund. The cost of all shipping will be your responsibility.
These are in addition to your statutory rights.
Contact Us
Please feel free to contact us through Ebay messages.
